Bonneville America Forums Forums Technical Forums Performance Mods Keihin CVK40 - Where The Parts Do Their Part

Geez, I spend most of the time on my iphone last night typing in info about the settings and all I get is talk about the lift. Typical.

I'm not a boaster and certainly didn't want anyone feeling jealous. That wasn't my intention at all. Purely wanted to express how good it was to use.

I think we all know that sitting on a stool and even with a normal lift, the bike still isn't hight enough. Well let me tell you, seeing into where the carbies bowl screws were without having to get on my knees and even then being hard to see, was pure bliss.

Most would know I have a back condition that I manage day to day but none of us are immune from wear and tear. So having Ferdie right up there, it's like a whole different world what you can see.

Yeah, I know, now I'm bragging. Can't help it. I suppose if any of you do come into a bit of extra cash, these stands are the epitome of luxury.

Anyway, I'm out to the garage to start up ferdie to see how how my pilot a/f mixture screw tweaking goes. With luck it won't take long and this will be the best I can get my bike without adding an A/F plug into the crossover pipe.

Actually, I'll create a new post on A/F gauges in the not too distant future cos I've decided Ferdie will be my bike for as long as possible. I just don't need anything else. He's perfect imho

I'll let you all know how he goes once tweaked and the carbs synced

I've just put Ferdie on the stand, opened up the idle mixture screws by one turn, opened the choke to 7/8ths, turned him on and pressed the go button and brooom.

Turned off the choke and increased the idle a bit and he's already purrring like a tiger. Love this bike.

Time to update that signature, eh?

Yes Ken I'll do that now. Thanks for your help too. Actually, thanks to everyone who contributed, I always appreciate and respect everones opinions on here. This Place is like a family of sorts to me and Ferdinand, cos I rely on him, he relies on me and both of us we rely on you guys.

Anyway, both carbs ended up being adjusted out by 1 & 1/4 turns each which when you think about it nearly is nearly in the middle before needing to go up a pilot jet size.

I just knew once I started Ferdie up that the 45's and other settings were close to spot on. I still really want to get an A/f gauge though cos eventually I'll be looking at "Upgrading" (no not to a t-bird ya gooses, we've got the best all round bike there) with different cams and an improved head etc, so it'll be invaluable for that too.

Thanks for the compliment too Dave but I think your bike is a cut above my friend. And all power to ya cos it's not hard to see those out there that have the gift for doing things right. Btw, fwiw I'm a proud Union Man too

Btw, I didn't get a chance to test ride Ferdie cos it's been raining here today but I know once I've dialed in the a/f and synchronized the carbs, the rest always works fine.

So now I'm ready for my next ride north and can't wait to get on the road.

Cheers
Stacka

Stacka, Let us know after you have had a test ride.

If you have a look at my signature you will see my set-up. I also run 45 pilots and have to have 3 turns out, if not a get a lot of popping on decel.

I have standard needles and no shims, I was wondering if I put a shim under each needle will that effect the a/f mixture on overrun? Also would I be able to turn my mixture screws in a little.

I have heard and read all the comments about plug colour with the unleaded fuels we run today, and I still think I am lean in low and mid throttle. Last time I pulled my plugs they were still light grey with no noticable tan colour.

I went from 150 mains to 155's and it certainly improved WOT, and mid range was the same. (Plug cloour didn't change)

I run the 790cc with the different cams.

Hi Frank, I'll let you know about the popping if any when i get a chance for a ride. I'm thinking I won't have much if any though cos I have had these settings before believe it or not but What changed things was my removing the restrictors and as we know, this helps the breathing which in turn may create some popping compared to previous times.

On the other side I've also disconnected the TPS and have a blank cap to tidy that part up, and some believe doing this helps reduce popping. For me I didn't notice any real differences one way or the other to be honest other than looking better and removing another piece of useless wiring.

IMHO though, straight off the bat I'm thinking a shim and 150 mains may be also be a better setting arrangement for you as otherwise I would have done them like yours. I have been wwwwwwwrong ( very hard to say that word : )

In the meantime, I find one good indicator to determine whether I'm running lean or rich has been fuel consumption and I can tell you thruxton needles ARE thirsty. So if you can or have info on your consumption will help you just as much and maybe even more than plug colour.

I'll be in touch but the next few is forecast for rain so it may take a little time before I jump on Ferdie for a ride.

Cheers stacka

Hi Stacka, Great minds think alike.(Mains & Shims)

I am going into town today if I can get through the water and road closed warnings. It;s bad enough dodging the idiot car drivers, but when you have to look for potholes on every bend it has got beyond a joke.I will pick up some shims from our local bolt shop. If he is back in business after our floods.

You said you are coming up to Bribie later this month. Be aware that all the roads in Northern NSW and Southeast QLD are in a real state. Just South of us at Gympie and Maryborough are currently flooded and all the roads are closed going South.

Jo & I had planned to be on Bribie at the end of the month, but who knows with this rain. My bike has been out of the garage once since Christmas. Did a whole 60 Klms. before I got soaked.

If everything clears up we will probably be down there.

Thanks for the heads up Frank. I've been planning on riding a lot of the back roads inland this time instead of the newell or New England Hwy's. I've done them more times than I can count but I will check road conditions before I go. 

I've decided I'll be riding regardless of the weather and even if all of NSW is pouring with rain I'll just take it easier and stop earlier, meaning when I leave today fortnight, if it takes me 4 days to get up there then so be it. I find whilst riding in the rain isn't as ideal as riding in the good weather, I love getting on Ferdie regardless. Sort of gets the adrenalin flowing more which equates to a certain amount of excitement. I really want to ride these back roads though but I can change plans on the run depending on whatevers going on at the time. Can't wait. 

(i wrote this today at work and copied if before goingon a call) I'm actually sitting in front of Ferdie now where I have it parked in the engine bay at work. Turns out it was fine this morning so I was able to ride to work instead of drive like I thought. Now whilst it's only 3 klm's to the fire stn from where I live, it was still long enough to test out the new carb settings and as predicted, blo#dy beautiful mate. You've gotta get a shim on each of those needles . No popping at all.

Back home now and the end of the day and saw the news about Toowoomba. I lived there for six years and that flash flooding must have been insane as my daughter puts it.

Anyway. fingers crossed this rain that has gone on for months stops. We'll see soon enough I guess.

Apologies to all our overseas members but Northern Aus has had historically high flooding which comes not long after ten years of drought.

Really tragic stuff.

Hi Dudes and dudettes, well I'm in Queensland now after riding 1360 Kilometres with part of a new route than normal to make things interesting. The ride was great. No rain and not too hot except for a few 100 Kilometres at 38 degrees C.

Now the report on my latest settings. To remind you I went from 42 pilots, thruxton needles and 145 mains to, 45 pilots, oem needles with one shim and 150 mains.

In a nutshell whist Ferdie ran very nicely with no problems at all, he felt a bit more sluggish going from cruising to wot. The other factor was the fuel consumption was higher at first than would have liked but it did improve the more K's I did.

So, as suggested by Micah I took my jets and needles tweaking kit to change the settings whilst up here which I'm going to do.

So I've re-read the comments and suggestions but I'm yet to have a look at my new iridium plugs cos I don't have a long shanked 18mm socket with thinner side Walls to remove the plugs for a sqizz at them. Tomorrow I'll take a ride and get one and see how the plugs look them for some clues, but for now this is what I'm thinking.

Ken's comments with his having used an air / fuel ratio gauge suggested the TBS needles may have been an option with lower main jets which I'm now thinking (hoping) may be my next strategy.

I also understand the mains don't get as much "air time" as the needles but as we understand are all interconnected.

So for now unless someone can convince me otherwise, I'd like to try the following;

Keep the 45 pilots (they'll be staying from now on), TBS needles (no shims) and 140 or 145 mains.

I'm hedging in the 140 mains direction. I know this has been a bit of a trial and to be honest it feels like I'm taking pot shots in the dark but until I get an air fuel ratio gauge or take the time for the one at a time approach, this is my next best option.

Any comments as usual are always welcome.

Good to see that you arrived safely in Queensland.

I've just read your report on your setup and am a little sceptical about you going down to 140 or 145 mains.

My setup is the same as yours with the exception of mains. I am running 155's.

I have found my fuel economy to be 20 Klms. to a litre.

I can bounce the rev limiter with no lagging when I go to WOT.

The major difference I have is that I have the 790cc engine with the hotter cams.

When I ran the 150 mains I got the impression that I was running weak. When I pulled the plugs they were more white than grey that is why I went with the 155's.

Now they are dark grey.

How long will you be on Bribie?

We are planning on riding down on Wednesday, we are waiting for the final reports on this new cyclone before we commit.

Hi Frank, thanks for your sentiments buddy. Yeah, arrived on Wednesday and my daughter and future Son in Law with the help of the families put on a superb engagement party. So now it's relax time etc.

I'm taking a ride over to Repco at Caboolture tomorrow to see if I can get the right socket to extract the plugs and see how they look. That should be a good start to guide me on which direction to go. To be honest I would prefer to have your cams as that changes the equation somewhat I suspect.

Because of that and as I've got time I'm going to give the TBS needles a go mainly due to how much I loved the thruxtons and how well they went albeit them being too thirsty. The TBS's are a bit in between and I hoping with the smaller mains, the various components will work well for Ferdie.

Gotta go cos dinner's on the table but I'll talk later about perhaps trying to meet up on Wed for a beer at the Bribie pub with Boof. I'll text him later to see if we can arrange something.

Stacka

Well All and in particular those that provided valuable input such as Ken, Chad, Micah, Frank, Steven and Ian, I think for my purposes I may have finally cracked the CVK Carb Code

I don't know why but I believe I was more on track to get better settings when I first started this thread. The three Amigos above were also backing up my own theory but for some reason I got cold feet and decided to change my settings to one's a tad more tried and tested.

My main reasons for this was, I didn't want any issues on my ride north and whilst my bike ran well, I was disappointed with both the fuel economy and the midrange power to wot.

So Micah's idea of taking my jetting kit up with me was a beauty.

To refresh your memories, I initially was running 42 pilots, Thruxton needles and 145 mains (I pretty sure that was it). I then intended to change the Thruxtons for the less thirsty TBS needles, swap the 42 pilots to 45's and seek advice on what mains to use.

Then even after many of the best replies intimated I should look at richening up the idle and mid circuits and leaning out the mains, I woosed out for some "Nigel Nobody" approach with 45 pilots, shimmed OEM needles and 150 mains.

So today I went back to plan A and this time kept the 45 pilots which are pretty well standard with open pipes and filters, used the TBS needles and as had been suggested, trying a smaller main jet and in my case i decided 140's were in order.

Well the improvement wasn't just noticeable on the butt dyno, it was something else all together. For instance I knew the Thruxtons were good for mid range, but the current combination I have now all seem to mesh in the way we all want ie. pulling reals strong from start to redline and even then wanting to go on with it.

I'm telling you all, Ferdie is now finally playing in a completely new ball game to what he's shown before.

So there ya go. It took a while but fingers crossed the fuel economy picks up now to verify these settings and the spark plugs similarly:


stacka

Are you or did you change one thing at a time? I'm glad it's working out for you!

The truth to your question Steve is no. I know that's been the method many believe is the best way to go but I just don't work that way. We all know the jets and needles overlap and in effect work as a unit, albeit each have their own area of responsibility so to speak.

So I guess I've taken the attitude of trial and error where sometimes I've simply increased the main jet size by one increment, whilst in this case I've nutted it out given the results recently. Of most merit though were some of the comments from others. For instance one comment suggested how it was believed our bikes actually respond better to larger pilot and mid range settings with lower mains in comparison.

For me that required a mind shift of sorts however their is no doubt the butt dyno results speak for themselves and now I'm wanting to know why I didn't go down this route earlier.

In saying all this though, I reserve the right to continue to tweak if I get a poor economy rating or the plugs look scarilly white in a few weeks. Stuff like that. I also really want to get an air fuel ratio gauge which will make jet changing less guess work and much more reliable in the future when I start doing the more serious power improvements.

Hi Stacka, we didn't have a lot of time on Thursday night to talk about set-ups so here goes.

Being a motor mechanic by trade and having a good friend who is a Harley/Triumph mechanic we have a reasonable amount of knowledge between us. (Concerning the internal combustion engine) He has 2 drag bikes that he races whenever he can (although they have Harley engines) they are carburettor fuelled so his knowledge of carbs is invaluable.

I have read on this thread and other threads about needles and jets, and some people do have the wrong idea about their relevance. I have tried to glean out any information from the Bonneville Website that I could so that I would have a starting point for when I did my FREAK.

After sitting down with my mate and discussing what I should do, we came up with the following. (Serving my apprenticeship didn't set me up for the information that came my way) this is from his experience, not mine.

Pilot jets are working all the time, they are feeding fuel all the way through the throttle range. (From closed to WOT)

Needle jets are working until they get to the stage where they can let no more fuel through (where they become irrelevant)

Main jets are where the major problems can be had.

To small a main jet and you will get fuel starvation in the throttle range where the main jet will not feed enough fuel to the needle jet.

To large a main jet and you will get an over supply of fuel after the needle jet becomes irrelevant (after the slide has reached its limit). Prior to that any size of main jet is OK as long it can supply enough fuel to the needle jet.

He said that the shape, length and thickness of needles is where the problems can become noticeable.

I hope that you can understand what I have said, I find I can relate information verbally a lot easier than written.

As an after thought I will give you the following regarding my set-up. (Whether it is the best for my 790cc engine I don’t know), seat of the pants can tell the wrong story.

Economy wise, Jo & I rode home from Bribie today and here are my fuel economy figures. (My signature gives you my set-up).

5.25 Litres per 100 klms. 45 MPG (US). 53 MPG (Imperial) that was cruising at 110 – 130 KPH for 3 hours. All up weight of Jo and I and luggage 180 Kgs. (380 Lbs).

Whether I try Thruxton needles, I don’t know. (Seat of the pants Dynos can be very confusing). I very rarely run my bike over 5000 RPM as I feel I don’t have to.

As you know my bike is set-up for 2 up riding and I can cruise all day at 110 – 130 KPH, so why flog it when there is no need.

Just as an afterthought my mate told me from experience that as soon as you start introducing High Compression pistons, hot cams, oversize valves and reshaped and polished ports, the whole ball games changes.

Any way Stacka I hope the above information helped in your endeavours.

I imagine some do not agree with the above, so be it.

Just watch out for that seat of the pants Dyno, the result might not be what you think.

You guys may well be right but like most of us I don't have an a/f ratio gauge (yet) so for me I keep plugging away until I believe I've got this right.

The thing I have going against me most is, I'm not seeing much dyno info or a/f ratio data from other riders with staintune pipes with the restrictors out and 865cc cams but I could have missed a post here or there.

If on the other hand I had SS, Bubs or thunderbikes pipes for instance, I would more than likely have more definitive data to base my starting point on. I don't though.

Of course I could also get a dyno done every time I tweaked but we all know that would be dumb.

Anyway, given my relatively rich leaning fuel consumption results on my ride up here and the fact Ferdie just didn't have that get up and go I know he's capable of from midrange to wot. Otherwise I probably wouldn't have felt the need to change settings again up here. If you're both right though and I'm not doubting your opinions either, I'll have a pretty good idea if I am running rich on my first fuel refill.

More importantly I can compare my settings I just changed which as I've mentioned wasn't too flash.

I also think we should not forget what you find as good settings will not necessarily be good for me cos of our different cams. Can anyone give good comparisons where we've both got the same settings but with us running different cams for instance. I don't think so.

So all I can do is listen to other's experiences, which I might add there is no specific concensus on, and attemp to combine it with a "read between the lines" trial and error approach.

Regardless Frank, from memory (what memory ha ha) your explanation is the first time since I've owned my bike the operation of the various components of our carbs has been explained that way on here but it is explained much the same in an aricle in our Tech' Vault. Certainly interesting to be refreshed on the technical aspects of the CVK's too.

So into my database goes your theory that you believe I may be running too rich in the middle and too lean on Ferdie's mains. I'll certainly keep your opinion in the back of my mind should my latest tweak still not be quite right. .

If I was going to comment in your theory though, I guess my main area of comment would concern where the majority of my riding is done ie, more mid range and generally only above 3/4 throttle for overtaking quickly or accellerating up large hills. That being the case, all I can say is since my last tweak both my mid range and above 3/4 throttle ARE now definitively performing better than before. I'm not sure what you mean when saying butt dynes can be deceptive cos there was no deception going on in this instance.

One last point is regarding how much more torque the 865's have compared to the 790's and accordingly my Speedie being able to pull at lower revs. This again brings me back to the point where the mains aren't as relevant for the majority of riding which even if my mains were a tad small, it makes little difference as i don't go there as often and if i was lean there ( doesn't feel like it), I wouldn't be lean for long.

To better explain, here's a cut and paste from the Tech Vault article I was referring to;

"The Main Jet size has the most influence on quantity of fuel
delivered. Below 3/4 throttle there's little difference between a 136 and a 150 main jet. At full throttle there is a huge difference". Well for me now at wot, that sluggish get up and go I had with 150 mains where I couldn't even get Ferdie to wind out properly, has now been replaced with the opposite where he just wants to keep accelerating. Again, no deception happening mate, just pure fun.

To be honest, the more I think about it, the more I think we could be comparing apples and oranges with our cams and also, your bike being set up for two up riding.

That's the only explanations I've got.

Anyway, I think we can all agree getting this thing just right isn't simply doing this or that, which I suspect is why there are so many different versions like yours. Some are actually even the complete opposite (when talking main jets) as what you and your mechanic friend have suggested.

Time will tell I guess. Stay tuned

Hi all. Just a quick update from my last.

On my ride up to Qld On my previous settings, I averaged 6.1 litres per 100 k's.

After riding over 500 klm's today, I actually showed an improvement in fuel consumption averaging 5.8 litres per 100 k's and as mentioned, my bike's performance is far superior to my previous settings.

Provided this trend continues, I don't think I will be changing the TBS needles but tweaking the mains may be on the cards down the track.

One other factor that hasn't been mentioned in this thread is, how the counter or small front sprocket effects overall fuel consumption

For instance, does anyone have any fuel consumption data regarding pre and post sprocket changes? I would expect going from 17 tooth to 18 tooth would give more K's per litre would it not?

5.25 Litres per 100 klms. 45 MPG (US). 53 MPG (Imperial) that was cruising at 110 – 130 KPH for 3 hours. All up weight of Jo and I and luggage 180 Kgs. (380 Lbs).

Thats on a 790cc engine riding 2 up.

When I ride solo I usually use about 5.1 Litres per 100 Klms.

With my current settings. Also a 18 tooth front sprocket.

Hi Frank. They are good consumption figures of yours for sure. No one is doubting that. My last reply was mainly in reference too your comment believing I was probably running rich with the settings I changed to last week.

I believe comparing your bike to mine is only confusing matters here. We can talk about that later. In my last I was able to show my fuel economy has improved with my new settings and as I've already mentioned my bum dyno tells me I'm not touching these new settings as before Ferdie was sluggish midrange to wot. Hey, my midrange is that much more responsive now I rarely have to open up the mains.

In short, my fuel consumption is showing I am running leaner (not richer) and, these new settings are more suited power wise to my bike. I was just responding to your suggestion Frank.

Regarding comparisons between your consumption stats and mine, what's the point?

You have 790 cams and 18 tooth counter sprocket and I have 865 cams and 17 tooth sprocket. You ride too up and I ride one up. Where are we going here?

I personally am not in the business of comparing my bike with others. It's a no brainer mate. I've responded to your original suggestion and as far as I'm concerned with Ferdie, he's running like a champion. I do however have a new chain and sprockets I purchased from "the chain gang" before they went broke (they only sold quality), and I'm waiting for my current ones to wear out. That's when I'll be able to put on the 18 tooth counter sprocket sitting there and with it, improve my current fuel consumption specs. Until then:

I didn't think you were running rich, Ken thought you were running rich in the middle and lean on top.

I also think you would get better figures with a larger main jet.

You should get your self an A/F gauge or bring your bike to a dyno. At lease get a base line to see where your at and what areas need to be tweaked. Checking your spark plugs after a ride won't tell you much but the overall average of the A/F ratio unless you held the motor at a targeted RPM range for an extended period to get THAT color on the plugs an then pullover and then check the color with out going into another "RPM" range.

Frank, after re-reading this epic thread, you're right about not saying you thought I was running rich in the middle. To be honest this thread has been a "head Fu**".

There are so many different variations of opinion which combined with different bikes, settings that work for some but it would appear wouldn't for others, it's an mine field.

So I apologise for reading your thread incorrectly and I do appreciate your and everone else's opinions. The good thing about this thread is, it's taught a lot about what the various roles each part has to play which btw is the subject.

In saying that I've tried to pick the info from the various comments that to me sound like will work best given my experience. So I've done that and I believe with the help of everyone I've more than achieved that objective given the improved Performance and fuel consumption.

For now then I'm happy to keep my settings the way they are until I organise an A/F ratio gauge, where I can more accurately diagnose "what's wot in the melting pot" lol

Thanks again for everone's contributions. You really helped me thoroughly enjoy my ride home with the extra power and economy compared to my ride up to Qld. Can't argue with that.

Thanks Steve. I've read about the process for more accurately diagnosing plugs etc but for me I'd rather just look at the plugs as a general sign they aren't white looking which btw happened once but not for long.

Because I enjoy working and learning about my bike and in the future to ideally go down the more expensive power improvement route, the a/f gauge is now on my radar of purchases (amongst other goodies ).

So for the time being I may try increasing the mains but it's not a priority and once I've got the a/f set up and happy with the readings, I'll probably get a dyno done then. My dyno op only charges $100 and considering I'm using the same machine and operator, it will be interesting to compare my last dyno results to see if all the work (not really work -let's call it fun) has paid off.

Stay tuned
Stacka