October 25, 2012 11:56 PM PDT
I ride an '86 Evo Sportster 883/1200.
What is causing my engine to surge? It's worse from 35-45mph in 3rd & 4th gears (4 speed tranny) while cruising.
Could it be the ECM?? Or out of time, causing a wrong signal to be sent to the ECM??
I put a newly tuned CV carb on it a while back.. Runs great except for surging....
I noticed the surging after replacing the clutches...
October 26, 2012 4:13 AM PDT
Is it only while riding?
Does it idle evenly?
If you hold the throttle at around 3,000rpm in neutral does it hold that rpm, or vary?
October 26, 2012 9:12 AM PDT
Had that problem once with a sportster.I had taken the carb off.Found the rubber boot between the carb and the intake was out of place.
October 27, 2012 10:57 PM PDT
The rubber boot is fine.
I will test it when the sun comes up Lucky.
October 28, 2012 12:13 AM PDT
Surging is usually caused by varying fuel air mix. I do not see what clutch change would have to do with it unless you disturbed something in the fuel system when doing that.
October 28, 2012 11:52 AM PDT
besides the rubber seal on the back of the carby there are also rubber seals where the intake mounts to the inlet...check the seal that they are intact and not broken...oh and by the way they are a royal pain in the rear end to replace...get a good night sleep and take your patience with you when you start...you'll need it!
November 9, 2012 6:46 AM PST
It could possibly be the new clutch if the engine revs slightly when applying power especially in the higher gears it could be a little slippage in the clutch. Have you re-adjusted the clutch since install?
November 9, 2012 6:51 AM PST
That was kind of my though when he said only while moving and he put a new clutch in.