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Poor Idle

  • Thread starter Thread starter Anonymous
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Anonymous

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Hopefully someone can help me out my 1978 750E is becoming very aggravating it will run great when cold but by the time I get from the parking lot to the end of my street about 2/10 of a mile it runs horrible obvious that cyls. are not firing and I have to give some throttle to keep it running but while driving seems to have plenty of power when you go up hills it tends to bog down a liitle, and will not idle it will die if you don't give any throttle at idle but will restart, both coils checked out ok I did find a main jet missing resync. the carbs complete tune up,replace the jet, have checked the plugs not much spark very weak, and this is the 5th set of plugs in about 3 wks that I have owned the bike the only thing I have not checked is the compression it sounds like a compression problem, would like a second and as many possible solutions as possible. Thanks in advance
 
Poor Idle

Did you completly tear the carbs down for cleaning? If not you could have some holes plugged. Does it run better with the choke engaged? Does the 78 have points that need replacing (someone here will know that answer)? Are your plugs burning out due to lean condition or fouling in oil?
Hopefully these are questions you can consider. Checking compression is a piece of cake. You should be able to rent/borrow/beg/steal a compression checker. Buying a good one shouldn't be more than 20 bucks.
 
Thanks DallyR I have done the carbs that was the first thing I did because it did act like a fuel problem,and I also gave it a complete tune-up points,condensors,plugs, removed and cleaned, and reoiled air cleaner,reset the timing,I don't know what the guy did to it that I bought it from, because when I sync. the carbs you could see the factory seals on the adjusters were already broken,he said it had an electrical problem but I have found everything but. I recently went out to start it to check some other things and now there is no spark in any cylinder and obviously it does not start, it cranks and that is it.
 
Wow......Maybe there is a serious electrical gremlin after all. I'm wondering if your mechanical ignition system is getting any juice or if it is, is it sending a signal to the coils to fire? I couldn't suggest any troubleshooting procedure to check that. I haven't had to look at mine and its been years since I've owned a 4 wheeled vehicle that didn't have electronic ignition. Surely someone on this forum will know an answer, or at least a direction, for you to try.

Best of Luck
 
Thanks dallyr I do appreciate your help I spent 8 yrs as an auto mechanic but have not seen anything quite like this before. Thanks again
 
I would suggest rechecking that coil.. Sounds to me like you may have a bad motor ground.. or the coil checks out under load but it is actually shorting out when you turn the engine over.. thats my 2 cents and I am now professional.. but one thing I do know is electrical components... also, check your plug wires.. they may appear good but could have a broken connection inside... the heat from the motor can do cruel things to plug wires.. I am replacing mine with high performance plug wires for high heat..
 
Your poor idle problem

Your poor idle problem

I own a 78 GS750 and have spent the past 12-18 months (on/off) rebuilding it. The biggest probelm that I had was with the carbs. My carbs are very sensitive to adjustment and any changes that you make should be very small ones. Firstly, are you sure it is an electrical problem you are having, not a fuel problem. How do you know it is a weak spark, to the naked eye it doesn't look all that bright anyway. If you are sure that its a spark problem I strongly suggest you don't spend too much time investigating. Do what I did. New regulator/rectifier, new coils, new plugs and a Boyer Brandsen electonic ignition unit. Rip out the points and bob weights, install this super little black box and away you go. Its fantastic. If you don't want to spend, then check your regulator/rectifier unit and battery. Basicly, is there 14 (ish) volts on the battery with the engine running and is the battery in good working condition. If the charging system doen't function properly, you will not get a good spark. If you suspect it is a fuel problem, and this is my first thought, then COMPLETELY strip down your carbs and have them cleaned in an ultrasonic cleaning unit. Very cheap and very quick. With mine, there was corrosion in the cast idle jets, there is no way an aerosol cleaner can get to those hard to reach places. Rebuild and replace the carbs, adjsut the idle screws/fuel screws as required and synchronise. It is a VERY time consuming and sensitive operation but WELL worth the effort.

I hope this is of use to you. If you have trouble getting parts, try the UK company "M and P". They are at "www.mandp.com". They sell loads of early 70s stuff, all pattern parts, all at reasonable prices. Coils, points, plugs, regulator/rectifiers etc. etc. etc. The deliver world wide.

regards
 
Thanks to all apreciate all the input did some extensive harness searching this morning and found a bad wire in the white and black wires that send to the coils made the repair, replaced both wires new connectors, and some minor carb adjustments and now its like new. Thanks again to everyones input
 
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