Bonneville America Forums Forums Technical Forums Performance Mods FCR 39mm

I'm going to do the big bore as soon as my valves show up...then do the carbs after buttoning it all back together, easy enough to do at a later time. I really didn't want to pull the stock carbs off and put them back on. Maybe yours will be available in the next 6-8 weeks Pat???

Thanks Pat,

Now that I'm "up to speed" on the subject I can't wait to see the end results.

One question though- Excuse my ignorance but what advantages is there to these carbs over a modified stock carb (ex. drilled out slide, lighter springs,...)

Quote:

---

Maybe yours will be available in the next 6-8 weeks Pat???

---

Hopefully. I will work on them this week for sure. Really!

Jim,
The flatside carbs do not rely on a vacuum and diaphram to operate. Vacuum operated carbs therefore have an inherant issue with leaks and possible lack of vacuum due to many variables. On the flat side carbs, when you pull the throttle, it is directly linked to the slide that comes up with the cable - mucho faster response from the motor. The CVKs in our bikes are a good reliable carb, but there seems to be vast differences from one carb to the other.
The flatside carbs will allow for very precise balancing and tuning between the two.
Mostly, they make the bike go faster, quicker. The difference between cracking the throttle wide open with stock carbs compared to flatside carbs is very noticible. Take a look at Eds arms, they grew 3" longer this last summer. He almost drags his knuckles while walking now.
Just kidding with ya Ed!!

Dinqua, thanks again for your work and answers to my questions.

I'll be installing 2mm larger intake valves and 1mm larger exhaust valves. Do you think your carbs will be big enough with the larger valves? Man, I sure would like to spend less than 1400 on carbs and get similar results.

I'll tear my engine down in the next couple of weeks (or whenever I get the valves) and wait until it's back together to actually buy some carbs.

thanks again!

So let me see if I understand -no matter what mods you do to the stock carbs you still don't have the throttle response you would get out of the flatsides? Is that because ,like you said, the flatside are directly linked to the slide therefore when you twist the throttle the slide instantly moves, whereas on the stock carb when you twist the throttle you have to wait for the vacuum to move the slide?

Ok I'm a little slow

sweat,
No problem, the 36mm or even the 34mm carbs will provide plenty of gas for up to 1000cc or more. Ed has the 790cc still and has his jetted low, I will jet mine up about 3 sizes above his settings and there is still plenty of room to go. I beleive the main jet sizes run from 90 to 275 if I'm not mistaken. Ed has something like 150s in his now. The pilots are the same, from about 30 to 80 in size. Needles, tons and tons of sizes, tapers, daimeters, length, all with the movable clips on them as well. I would pretty much call them unlimited tuning range.

how much harder are they to jet than the stockers?

Frank

The main jets are easily gotten too by just dropping the small plug on the bottom of the carbs, pretty easy.
It's the needles that are a bear.
The big springs that work the slides need to come out if you want to do needle adjustments. That's a fun job - whacks my fingers good everytime.

here's A link to the TM carbs with all sorts of pictures and arrows and glossy 8 by 10s.

BIKER

Hey Dinqua, I just ordered my Wiseco 904! I've been talking about ordering it for a couple of months and finally did...waiting on the valves, and as soon as they show up it's teardown time! Thanks to Brent, and barring frozen streets, I should have the Wiseco kit tomorrow.

I'm very intrested in seeing a end resulting dyno comparison between your bike with stock carb's and your bike with these carb's mounted up using a real world a/f ratio.

Also, since your attempt to make it down here for the TCHR last year wasnt successful, will you try again this year?

Lot's of pretty country to ride down here, our local pack asked if I would lead a ride.

I will try to get down again this year. I have an ex-brother in law that rides from Texas for it as well and he comes every two years. This is the year he's coming again and I like to hook up with him and ride with him back up to NY where his family still lives. I'll know when the time gets closer.

Hi all, this is a great thread guys with some really intereting stuff there. I really appreciate all the free flowing info on how to get better gains and by the sounds of it, the 36 mikuni's flat siders are the go. To Pat, I'm (like many others I expect) really interested to see how you go once you have your's installed. Maybe that dyno voucher I sent you (I am firie9 on ratnet) will be used get a good comparison between the cvk's and the 36mm mikuni's. So maybe I am helping in some way to help you and then us determine the best options. Anyway, I was just wondering if you were going to give good step by step instructions (like you did with the cvk's) on installing the mikuni's? I don't think I will be the only one who would be grateful.

That was the plan for the dyno slip you sent to me John, thanks again, it will go to good use.
It was way too cold for my girlie hands to work in the garage this last weekend, I'll get back on the carbs this week for sure though and take some pix as well.

Great stuff Pat, and there's no need to thank me cos I appreciate that it's being used for the common good if you know what I mean. Anyway, of course there's no rush with the cold over there and all. Just take your time and when you feel like doing it, you'll enjoy the process that much more.

Just for interest, I found this site with the TM series flatsliders (scroll down the page) and it has a good diagram of all its parts

or just click this for the diagram Keep up the good work fellas

pulling this back up hopeing Pat has them on now

I've read lot of tuning tricks and dyno compares all around the net and in tech magazines,

lot of technicians have been able to extract from a tuned CV carbs a power very closed to flat slide carbs.

If you have good knowledge of the CV technology maybe you'll know all the variables to change to make a perfect carburetion at every RPM range and throttle open.

For example lot of people don't know that the number and diameter of holes in the emulsion tube are responsible for a lean condition of mid-revs.

The transition from low-revs to mid-revs is the range used by EPA for pollution statistics, and the bike producer has to tune a bike for low pollution and noise in that revs most used in the city.
Idle and hi-revs are less important because they are used only when waiting on trafic light (short time for a bike) and outside the city (for high-revs).

I use to modify CV closing some upper holes on emulsion tube (using epoxy resin) to obtain a bit richer condition without raise the needle.

A well tuned CV carb has a top power only slighty less than a flatslide, but with a smoother operation and better low/mid ranges.

Yes it does get much more simple than makuni when is the last time ya messed with an Amal drip tube? I have a set from a Norton 850 commando I was thinking of putting on my SM. A Triumph should have an Amal!! I was hearing rumors that Triumph was in talks with Amal to supply carbs again but nothing lately.

ANALS !!!!!!!!!!!!!!!!!!! oh man????