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Surging/missing at constant throttle

Old 09-20-2011, 05:44 AM
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Surging/missing at constant throttle

Hi guys, new to the VTR, brought mine around 4 weeks ago and was wondering if you guys could help. My 98 model has been jetted and has pipes, and was tuned on the dyno some years ago. Issue- When on constant throttle it surges and misses, some times bad enough to make the chain ******, have done the basics, plugs, clean and sync carbs ect but cant put my finger on this. Bike is fine otherwise but i cannot live with this. Thank you for your assistance.
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Old 09-20-2011, 06:07 AM
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Carb Tuning guide (setting up a Dynojet or Factory Pro kit)

If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn increments. Alternative pilot jets are supplied when normally required.
Pilot fuel mixture screw settings, float level and pilot jet size also affect high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing pilot jet size will usually cure the problem.
or

www.vtr1000.org • View topic - Scorpions and Fuel

Scorpions and Fuel
by Mick B Thu Jun 03, 2010 2:20 pm

Ok just to round the post off the bike is complete.Put the emulsion tubes in yesterday and have done roughly 100miles and not one nudge fart cough nothing just perfection. At one point I thought of selling the Storm when the thing was surging etc but I stuck with it and now have a complete bike. So anyone who has surging,nudging etc on a steady throttle it could be the same as me . Dynotune, carbs cleaned set up with new emulsion tubes the bike is so smooth

Forgot to say the old brass tubes where not blocked but did have internal wear and slight ovalisation where they should be round.Hence running rich on steady throttle causing the surging etc.

Last edited by Wicky; 09-20-2011 at 06:12 AM.
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Old 09-21-2011, 09:30 AM
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Try going back to #45 pilot jets. More than likely you have #48 or #50's in there now. Seems like the jet kits recommend bigger jets but they have always caused the condition you are having. Going back to stock (#45) has done the trick every time for me. Good luck!
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Old 09-21-2011, 09:38 AM
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Originally Posted by JamieDaugherty View Post
Try going back to #45 pilot jets. More than likely you have #48 or #50's in there now. Seems like the jet kits recommend bigger jets but they have always caused the condition you are having. Going back to stock (#45) has done the trick every time for me. Good luck!
Kind of like the thread I posted. You can either change the mains or the pilots to correct the slight lean condition of a stock SH but not both, as that causes an over rich condition.
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Old 10-01-2011, 06:52 AM
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Talking

Hi guys, Thank you all for the info, I have stripped tha carbs again to double check everything, emulsion tubes looked in good nick, changed the needle to 2nd slot from the top, thoroughly cleaned everything again, got rid of the K&N filter. 1st ride since today, it has a shitload of grunt all through the range (nearly flipped it in 2nd) but the missing / surging is stilll there at constant throttle, if I feed power on gently it goes away, if I decelerate it is not there, it does not matter what revs- 180kph, 8000rpm in 3rd or 5000 in 6th at or even 40kph 2nd 1500rpm, misses and chain snatches (not good mid corner). Next step will be the no 45 jets like Jamiedaughtery suggested, I will let you know the outcome, again cheers for the info.
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Old 10-01-2011, 05:07 PM
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I am running the 48 pilots with the emulsion tube mod and have no issues going on 8 years.

Depends on air filter, pipes, Smog removal, jet kit needles, elevation, temp just ot name a few. Carbs also need to be in sync.
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Old 12-17-2011, 12:31 PM
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2500 rpm surge

sounds to me like your timing chain has jumped a tooth or two. try setting the timing.
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Old 12-20-2011, 05:48 PM
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DynoJet usually recommends the 4th slot down on the needle unless you happen to be at altitude.
I am at sea level and near the 5th slot on my DynoJet needles.

This would explain your lean surge -because the needles need to raise more and let fuel in.
What mains are you running and what's you altitude?

Edit: 8541Hawk is right. If DynoJet is in there, you should already have 45 pilots stock and only larger mains. Going up on both would be bad.

Last edited by Matt_Hawk; 12-20-2011 at 06:05 PM.
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Old 12-20-2011, 07:03 PM
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does it miss at idle?
when was the last time plugs were changed/checked?
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