nightmare yzf 750

pawearr · Post by **pawearr** » Thu Jun 30, 2005 11:46 am

Hi folks im having real trouble with my 750 r at first i thought it was the exup (thanks all who posted ) exup seems fine.problem is the bike runs like crap below 2000rpm very stuttery and jerky,carbs have been cleaned,checked,balanced no leaks from any hoses i put new plugs propperly gapped full service and no change,this is driving me nuts as i love this bike and dont want to sell it, all my local mechanics are stumped and the meter's still running.could the problem be overcooling as the fan is wired in permanantly to the ignition or would the current draw from the fan draw power away from the coils,the local mechanis told me the spark is weak at low revs and too high at high revs ????????????????????// help if you can any suggestion welcome.

ExupElvis · Post by **ExupElvis** » Thu Jun 30, 2005 5:27 pm

<blockquote>Quote:<hr>the local mechanics told me the spark is weak at low revs and too high at high revs ????????????????????// help if you can any suggestion welcome.<hr></blockquote> It's the alternator. I do believe those alternators have an internal regulator. Replace the unit and the problem should be solved. (The quick failure description is that a failed stator in the alternator will give an A.C. output signal to your D.C. electrical system. It doesn't know how to handle that, not to mention having the low/high output variation which is most likely killing your ignition at low revs). Try this to troubleshoot - disconnect the alternator plug. Replace your battery with a known good fully charged one. Go for a short ride. If the problem goes away, you have a definitive diagnosis on a bad alternator. Good luck on that........... Genisx1AtYahooeyDotCommaMomma

pawearr · Post by **pawearr** » Fri Jul 01, 2005 2:59 pm

hi elvis thanks for the reply,i got a new battery and tried disconnecting the alternator with no luck,could the problem be the pickup coil or the cdi or maybe the coils ?

dragracer1951 · Post by **dragracer1951** » Fri Jul 01, 2005 3:53 pm

did you charge the battery????????????????????? Jim <img src="http://img.photobucket.com/albums/v209/ ... Cheers.gif" style="border:0;"/> <img src="http://img.photobucket.com/albums/v209/ ... states.gif" style="border:0;"/> Hey Kid...Is my taillight working?

ExupElvis · Post by **ExupElvis** » Fri Jul 01, 2005 8:02 pm

It could be either CDI or pick-up pawearr, I don't know how to check a CDI for things like dwell time, but I do know it responds to pickup coil inputs. Try disconnecting the hardwired fan first, if it's drawing too much power it could be taking too much power away from the rest of the system. If that has no affect, I would start with a new pick-up sensor, as I have seen posts on those going bad and causing various weird symptoms. Don't give up though, it's not an impossible problem. Have a <img src=http://img.photobucket.com/albums/v209/ ... Cheers.gif ALT=":cheers"> and take a break for a minute, It'll pay off to take a methodical approach. Genisx1AtYahooeyDotCommaMomma

exupturbo · Post by **exupturbo** » Sat Jul 02, 2005 4:52 pm

Valve clearance? Mark

ExupElvis · Post by **ExupElvis** » Sat Jul 02, 2005 9:21 pm

<blockquote>Quote:<hr> Valve clearance?<hr></blockquote> Now there's a thought.................mixture will affect spark.......... <img src=http://img.photobucket.com/albums/v209/ ... Cheers.gif ALT=":cheers"> Genisx1AtYahooeyDotCommaMomma

exupturbo · Post by **exupturbo** » Sun Jul 03, 2005 1:07 am

Tight valve clearance or worse still no valve clearance will give bad compression at low rpm, I had a car that was a pain to start and ran rough at low rpm and it was down to the valves being too tight a clearance. Mark

Pete Aristocracy · Post by **Pete Aristocracy** » Sun Jul 03, 2005 2:20 pm

Me too had low speed problem which seem to disapeare with rev's but the engine was slow. It was trouble to start and then run VERY ROUGH!!!! Discovered no valve clearances at cold...<img src=http://www.ezboard.com/images/emoticons/devil.gif ALT=":evil"> But bike was in service on the begin of season and I was told that everything is fine..(Major reason for me to do maintanance by my own). Wish soon fix! Pete<img src=http://img.photobucket.com/albums/v209/ ... Cheers.gif ALT=":cheers">

Lemmy · Post by **Lemmy** » Tue Sep 13, 2005 1:05 pm

Hello - why in heavens name would anybody wire the fan directly to the key? If it is the thermo-switch being faulty, go buy a new one! Can you get the bike moving, when applying just a little bit of gas? I mean - like on idle gas only? Can you get the bike running when you rev it up to like 4-5k, and then slowly let go of the clutch? If yes to this, it is your emulsion tubes pretty worn. Regards - Lemmy

750muppet · Post by **750muppet** » Fri Sep 16, 2005 11:40 pm

I had an 04 R1 doing a similar thing at work the other day.... the throttle position sensor was not playing the game..... Steve

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