GSXR 750 ( 1986) problem with a miss - Motorcycle-Journal Forums

oceana · 12-27-2003, 04:09 PM

We have a problem with our GSXR 750 which has a miss at low revs - if revs are over 7000 the miss is very slight but under this its very bad - it seems slightly better if the bike is cold. Its is slightly better if the throttle is eased up slowly. We have had the bike to the dealership and they cannot find the problem they have checked plugs - leads - carbs etc
Any suggestions oh how to find the cause of this problem would be appreciated - Thanks

**87gsxrnut** · 12-29-2003, 04:40 AM

Check the coils. These are notorious for going bad on the old Suzis. You can do a heat spot check by touching the pipes (with a towel - don't burn yourself) to see if they are putting out like they should. Pipes 1 & 4 are on one coil and 2 & 3 are on the other. Heat should be the same across all pipes. You can also use a laser heat testing gun to check this. I don't have my manual handy for the ohm numbers, but you should also check the coil resistance as well.

Check the harness wires that connect to the coils too. Sometimes they get corroded (I just lived through this on one of mine). Clean them if needed. Also check for a loose fuse. Try spraying some electrical contact cleaner in your ignition as well. You can get it at Radio Shack.

Is this a true miss, or is it sounding/running a bit rough? It might also be a fuel delivery problem. Check your vacuum line from the carbs to the petcock.

Don't trust the dealer. Most mechanics these days do not have the experience or historical background working with the 1st Gen. Gixxers. They are a quirky lot to be sure.

- Ross

oceana · 12-30-2003, 12:13 AM

Thanks for that - will try your suggestions - really appreciate your advise

**87gsxrnut** · 12-30-2003, 03:24 PM

Let me know how it turns out. I have some other suggestions once you try those I have mentioned above. As with any old bike, there is usually a multitude of problems that go along with it due to age, abuse, neglect etc. It sometimes takes time and a lot of patience to sort all of them out. Plan to replace all of the fuel and vacuum lines in addition to inspecting/servicing/replacing the following at a minimum:

Forks (change the oil and seals)
Brakes (bleed master cylinder/calipers)
Clutch (bleed master cylinder/slave cylinder)
Chain and sprockets (replace if worn)
Valve adjustment/Retorque the head (probably the most important service on this motor)

- Ross

12-27-2003, 04:09 PM	#1 (permalink)
oceana Newbie Joined: Dec 2003 Location: new zealand Posts: 2	GSXR 750 ( 1986) problem with a miss We have a problem with our GSXR 750 which has a miss at low revs - if revs are over 7000 the miss is very slight but under this its very bad - it seems slightly better if the bike is cold. Its is slightly better if the throttle is eased up slowly. We have had the bike to the dealership and they cannot find the problem they have checked plugs - leads - carbs etc Any suggestions oh how to find the cause of this problem would be appreciated - Thanks

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12-29-2003, 04:40 AM	#2 (permalink)
87gsxrnut Ho Dog Joined: Dec 2003 Bike: 867-5309 Location: Terror Lake Posts: 4,224	Check the coils. These are notorious for going bad on the old Suzis. You can do a heat spot check by touching the pipes (with a towel - don't burn yourself) to see if they are putting out like they should. Pipes 1 & 4 are on one coil and 2 & 3 are on the other. Heat should be the same across all pipes. You can also use a laser heat testing gun to check this. I don't have my manual handy for the ohm numbers, but you should also check the coil resistance as well. Check the harness wires that connect to the coils too. Sometimes they get corroded (I just lived through this on one of mine). Clean them if needed. Also check for a loose fuse. Try spraying some electrical contact cleaner in your ignition as well. You can get it at Radio Shack. Is this a true miss, or is it sounding/running a bit rough? It might also be a fuel delivery problem. Check your vacuum line from the carbs to the petcock. Don't trust the dealer. Most mechanics these days do not have the experience or historical background working with the 1st Gen. Gixxers. They are a quirky lot to be sure. - Ross

12-30-2003, 12:13 AM	#3 (permalink)
oceana Newbie Joined: Dec 2003 Location: new zealand Posts: 2	Thanks for that - will try your suggestions - really appreciate your advise

12-30-2003, 03:24 PM	#4 (permalink)
87gsxrnut Ho Dog Joined: Dec 2003 Bike: 867-5309 Location: Terror Lake Posts: 4,224	Let me know how it turns out. I have some other suggestions once you try those I have mentioned above. As with any old bike, there is usually a multitude of problems that go along with it due to age, abuse, neglect etc. It sometimes takes time and a lot of patience to sort all of them out. Plan to replace all of the fuel and vacuum lines in addition to inspecting/servicing/replacing the following at a minimum: Forks (change the oil and seals) Brakes (bleed master cylinder/calipers) Clutch (bleed master cylinder/slave cylinder) Chain and sprockets (replace if worn) Valve adjustment/Retorque the head (probably the most important service on this motor) - Ross

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