revtech backfire issue
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6th Gear
Joined: Sep 2012
Posts: 10
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From: washington
revtech backfire issue
Working on a friends bike so I have minimal info. J know its a revtech with mikuni carb. Cleaned carb and it looks great now. Problem is it runs and idles great, but when trying to accelerate it backfires badly and will die. No idea how long it has sat, if it ran good prior to this problem, etc. (Waiting for a text back still) I am thinking bad fuel or timing. Any suggestions where I should go from here? Thanks for the great forum and people on it!
change fuel and then check the ignition... rev tech are known to burn though ignitions... on the last one we did we had to machine out the ignition cover and put a screen there, so that it would get some air... also highly recommend compression releases or you are going to go though starters and/or batteries like mad
they pull apart pretty easy
they pull apart pretty easy
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6th Gear
Joined: Sep 2012
Posts: 10
Likes: 0
From: washington
Thank you! I changed fuel but same issue. I took right cover off. The electronic ignition is set at 0 on left dial, 5 on right, but I have no idea what should be! I am near positive it is ignition, just not sure where to begin of how to test it!
Outstanding HDF Member
Joined: Jul 2008
Posts: 2,115
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From: SoCal
When you cleaned the carb, were you careful not to clog any passages? Did you set it up correctly? Is the accelerator pump working properly? Is the carb as a whole?
Definitely flush that gas, clean the fuel filter (s)...me personally I'd run some Marvel too.
what about air leaks or vacuum leaks?
Outstanding HDF Member
Joined: Jul 2008
Posts: 2,115
Likes: 5
From: SoCal
Not sure how "of course" comes into play here. Most people are nowhere near meticulous. Not a judgement just an observation.
The problem you're describing seems to be a fuel delivery issue...carb's at the center of that, of course. But yeah, seems like gas, BUT...I had a bro who had a DTT nosecone module in his SPCN fxr-style bike...started gettin misfires here and there. Idled fine, revved fine no load, but when he'd get on it under load, actually riding, it'd start spittin flames bang bam boom! Nosecone module was overheating and going haywire and it would only show up under those specific conditions. He also had the timing all f-ed up cuz he thinks only dorks read manuals so he just "does it by feel." So yeah maybe timing.
Pretty sure RevTech ignition setups are based on the Crane Hi-4 which was notorious for being finicky AND overheating.
Have you considered the VOES if it's running one? Weird **** happens when they go froggy.
The problem you're describing seems to be a fuel delivery issue...carb's at the center of that, of course. But yeah, seems like gas, BUT...I had a bro who had a DTT nosecone module in his SPCN fxr-style bike...started gettin misfires here and there. Idled fine, revved fine no load, but when he'd get on it under load, actually riding, it'd start spittin flames bang bam boom! Nosecone module was overheating and going haywire and it would only show up under those specific conditions. He also had the timing all f-ed up cuz he thinks only dorks read manuals so he just "does it by feel." So yeah maybe timing.
Pretty sure RevTech ignition setups are based on the Crane Hi-4 which was notorious for being finicky AND overheating.
Have you considered the VOES if it's running one? Weird **** happens when they go froggy.
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Thread Starter
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6th Gear
Joined: Sep 2012
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From: washington
Of course as in anyone who works on carbs should be meticulous. I have dealt with a lot of fuel issues and this don't act like any before, so I suspect ignition. On that note I will definitely be going back thru the carb and fuel system just to be sure. Any suggestions if you believe it may be jet size issue? Up or down on size? It appears to be 100 ci running down sweep pipes. No baffles. Have had very little time to work on it so was kinda doing my trouble shooting from here. Thanks for the responses!
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Tourer
Joined: Aug 2010
Posts: 497
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From: Wa. state
Obviously, start with the most simple stuff first. ensure high voltage spark at both plugs, check condition of ignition wires and ignition timing . If all that checks out I would consider the valve timing, burnt, bent, or damaged valves. Then condition and propre operation of cams, cam chain, or gear drive. Trouble shooting is basically the process of elimination. Do you know what happens when plug wires are crossed up?