Bonneville America Forums Forums Technical Forums Performance Mods Carb Help

I decided it was time to do what a lot of other members have done, and replace my factory airbox with some K&N filters. It was a pain but I got everything put back together and took her for a test ride. The bike's running great, but I do have one minor concern. It seems like the carbs will randomly "sneeze", mostly when the bike's idling. It doesn't seem to effect performance or anything else, but I'd like to make it stop doing that if possible. They kind of pop and try to pull out of the rubber mounts. Fortunately, my carb brace keeps them in place when this happens, but it still seems a little off putting. Anyone have any ideas for me? Besides the filters, I went from 132/45 jets to 145/42 jets as I could smell gas when I was idling with the 45s in and got sick of people commenting on it. I also adjusted my air mix screw to 2 turns out from 3 turns out. I figure it's just a fine tuning thing and I've never had this problem before but thought I'd reach out and see if any of you had suggestions as to where I should start tinkering.

what kind of pipes?

Have you adjusted the mixture screws correctly or are you just picking a spot and running the engine?

I have short TORS that have been gutted. I screwed the mixture screws all the way in, then backed each one out to exactly 2 turns.

That isn't the way to adjust the mixture. Some guys do both cyl. at the same time but I find it easier to do 1 at a time and think it a little more accurate. Pull one plug wire and ground it using an old plug to the frame or a spark tester with a clip. Turn the idle up just enough so it won't stall. Turn the mixture screw in until the engine starts to run rough then back out until it runs rough again the correct setting is half way between those two rough points. Repeat for the other cyl. If the adjustment is 3 or more turns out you should go up a size.

EDIT: If you think this will take you much time it is a good idea to put a big fan or 2 blowing on the engine. Also as with any adjustment this should be done with the engine at full operating temp.

You need to adjust for the best idle. Simply picking a setting isn't really recommended unless you have mapped what each screw setting does to your idle.

Personally I think your needles are turned too far in. You might have been able to run with 2 turns out with the 45 pilots but the 42s, you will require a richer setting.

As for the rich exhaust smell, it is inherent with the bike. I have had several comments about a strong exhaust odour. Remember, we aren't running any catalytic converters and with minimal emission controls.

Thanks for the help! The mixture screws are the root of the problem, that much I'm sure of. I didn't know I wasn't adjusting them properly before. The_Dog33, I'm going to use your method, I was a fool to try it any other way. Gregger, I hadn't thought of the lack of emission controls adding to the rich smell. Maybe 45s are the right size pilot for me. I was worried about running too rich, so I think I'll stick with the 42s for now (stock on my bike were 40s). Once I get the kinks ironed out I'll probably run it on a Dyno before doing anything else. Thanks again, you guys rock.

using Dinqua's Jet Calculator ( Jet Calc ) as a guide and entering your info (Freak, TORs - gutted, sea level) it seems your low on the main jet.
The calc suggests a 162 but that'll prob be a bit rich.

As some of the others suggested, turn your screws out a bit more. Maybe 2.5 or try quarter turn increments. I can tell you on mine both needles are a bit off from each other by about a half turn.

On a separate note...you describe it as a cough. I hear that on my bike on occasion when shutting it down and if I did it while looking at the carbs I can see them move as you describe. Ive never had it happen while running. One time, before I had my K&Ns on tight it popped a filter off. based on this I had to assume it was a "burp" of air coming out the carbs. I'm not sure what would cause that but maybe someone else will chime in and hopefully head down the right road???

If you actually removed your carbs you might not have the carb to intake boots on quite right. Check those, they should be snug on both ends and the nib at the top. Also check those squirrel condoms (vacuum caps) and make sure they are all snug.

Captain M,
I'm going to throw my 2 cents in here on top of all the excellent suggetions you are getting.
Sync your carbs by the book.
Use the vacuum guage or tube method to make sure they are pulling equally.
Once you have them in sync, you can connect the front 2 vacuum ports with a length of rubber tube.
My engine really smoothed out at idle after I did this.

Thanks for all the great suggestions everyone. I adjusted the mixture screws as suggested and now the bike's running better than ever! It's sunny here in Seattle so I went for a long ride just now and didn't have a single hiccup so I'm feeling pretty relieved. I actually am planning on using my friend's vacuum gauges to sync the carbs, I just wanted to get it running right before going any distance. I am also aware that 145s are probably too lean. I also have a pair of 150s and a pair 160s which is what Pat's jetting calculator recommended, but that seems pretty big and I didn't want to be running rich after having that problem with the 45 pilots. Thought I'd work my way up. I also have some shims but haven't played around with those yet. I took the advice of switching the bowl screws to allen style, so swapping jets shouldn't be a problem. I had to take off the back tire to get the airbox out intact, and decided to upgrade to a 19 tooth sprocket while I had the chain off. Basically changed a lot of little stuff I was too busy riding to bother with when the weather was warm.

I bought a battery bracket from brokenfixed, and relocated the battery to under the seat. Using his prefab bracket saved me a lot of time on this project. It worked awesome, but I made a slight modification as far as the key position. I also removed that hidden fuel filter and put on a clear inline one instead, and upgraded the all the hose clamps while I was at it. I hope to have her in good shape for some long rides this spring. Thanks for everyone who gave me advice along the way.

Wow...sounds like you've gotten a lot of work in lately. I'm glad it sounds like you've got your carb issues under control now. The bike looks great with the bat relocation. What is the x shaped object over the carb in the second pic?

Choke lever knob. Someone on here made on from an old sink handle. I found one laying around a friend's house, gutted it, JB Welded a screw into it, and put it on. It works great when the weather's cold and I've got gloves on. I think it started off as a joke. It's been suggested that I should take it to the next level by hanging a pair of those metal tea balls off the bottom of the bike.

Is it the Hot handle? I think that's what it says.
That's actually pretty funny , yet, unique as he11 .

Yeah, it's the Hot handle. The one I was going to use originally said "Waste", but I had problems gutting it to fit the screw, so I went with Hot.

Yes,very nice choke tap.