HI, I have a 2001 Bonneville, I spent the summer cleaning it from top to bottom and upgrading parts. Mostly BC parts, exhaust, air box eliminator and AI eliminator. along with some cosmetic changes. I've changed the jets in the carbs and cleaned them, I've adjusted the idle mix screws and it idles and runs good. My local mechanic helped me with the jetting and has ridden it and said it feels good, no flat spots in the power band. Here is the problem every once and a while there is a "Blow Back" into the carbs from the motor, doesn't seem to be an explosion just unburnt fuel and air? Enough to cause the carb to jump off the carb boots if I didn't have the BC Carb Brace in place. My mechanic said it might be because its running a little on the lean side. I have pretty big Pilot and main jets in it now and granted it was being ridden in colder temperatures but could it be running lean? has anyone had this problem before?
Carb blow back?
- Thread starter Malen
- Start date
Keith Harding
Two Stroke
"Enough to cause the carb to jump off the carb boots"
Yikes!!!!
Yikes!!!!
Bonniebret
Rocker
I was getting some wicked backfiring through my carbs this summer. Lotsa lean pop too. Turns out it the top of one of the vacuum caps had rotted over time and blasted off. Dropped a new one on and it fixed it.
beemerrich
Street Tracker
+1. My CR carbs backfire after turning off the enrichener/until the bike warms in the early spring/late fall due to temps (sub-40 F) leaning the mixture.
bluesforchallah
Rocker
I had this problem as well, until I pulled the air mixture screw and Pilot jets. Using carb cleaner and compressed air, I squirted carb cleaner up the mixture passage until it came out the passage where the pilot jet screws into, then blew out the carb cleaner using the compressed air, then went the other direction from the pilot jet out thru the air mixture screw and again, blew out the carb cleaner with compressed air. Did this on both right and left sides. I suppose that with a clogged passage way between the pilot jet and mixture screw would result in a leaner mixture.
Also... It probably wouldn't be a bad idea to get a rebuild kit for the air mixture screw as that itty-bitty rubber o-ring can get buggered up. However, I'm not sure how accessable those mixture screws are on the '01 models. Don't they have some type of plug that needs to be drilled out?
Also... It probably wouldn't be a bad idea to get a rebuild kit for the air mixture screw as that itty-bitty rubber o-ring can get buggered up. However, I'm not sure how accessable those mixture screws are on the '01 models. Don't they have some type of plug that needs to be drilled out?
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fordtech48
Scooter
I tried to get those O-rings to replace on my mixture screws but Triumph only sells them with the mixture screws which ain't cheap. Anyone know where to get quality replacement parts for OUR cvk carbs?
bluesforchallah
Rocker
I got my rebuild kit thru CV Performance.
PM coming your way with link.
Edit: You don't have enough posts yet for PMs. http://www.cv-performance.com/cvp-mixture-screw-packing/
fordtech48
Scooter
Thanks, just ordered 2 kits for my carbs. Do you guys put the washer and o-ring on the mixture screw before installing it, or try to put the o-ring and washer down into it's hole then insert the idle screw?
When I took my mixture screws out, the washer and o-ring stuck in the carb.
When I took my mixture screws out, the washer and o-ring stuck in the carb.
bluesforchallah
Rocker
I slide everything onto the mixture screw prior to inserting it.
In this order:
spring
washer
rubber o-ring (on top).
fordtech48
Scooter
Yeah, that's what my service manual says, should have read it before asking a dumb question.
bluesforchallah
Rocker
No worries. It ain't nothing but a chicken wing.
Thanks everyone, sorry i have been away I have read all your input. It turns out to be the rubber boots and the clamps. I did some tests by spraying carb cleaner over the boots and the idle went up. So I took off the clamps and boots and found the clamps were bottoming out and not compressing the boot. I could twist the boots while the clamps were as tight as they would go. I got some tighter clamps and put everything back together and its running like a champ. No throttle delay no flat spots in the power delivery and no "Carb Blow Back". Thanks again
