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Help diagnosing issue/s.

  • Thread starter Thread starter DrunkenChekhov
  • Start date Start date
D

DrunkenChekhov

Guest
Well, I just yanked the carbs off and gave em a bath, re-assembled with new o-rings and put back on, and I'm still having issues. Two main ones, and I have absolutely no idea if they're related.

Issue 1.

The bike doesn't want to start. It'll crank and crank, but doesn't want to fire. However, sometimes it will fire when I release the starter button. If it ever does, its always on the release. The choke is working properly and I am getting gas to the engine (spark plugs are wet). The spark on the plugs is dim, quite dim. But I just replaced them not 3 weeks ago... Also, while one plug is out that I'm checking the spark on, the motor fires, what's up with that?

It'll also roll start, every time without problem.

Preliminary diagnosis seems like the starter is hogging up all the power, and the coils are weak and crappy and aren't sending enough power to the plugs. Could this be correct? Would replacing the coils fix this or is it a power distribution condition?


Issue 2.

Once the bike is driving, it's got a lot of power for about 2 shifts of time, then it wants to bog down, and if I twist the revs up it'll clear itself out. But if I'm just cruising it'll surge; power, lack of power, power, lack of power, etc.

Idle is sporadic, and will die if I'm not on the throttle while stopped.



So, oh great GSR, are these problems related? I had both when I started the carb teardown and was hoping it would correct one or both of these, but alas, my efforts were in vain.


Thanks for all the help guys, and a special thanks to BassCliff for his awesome website!
 
Hi,

Issue 1: My first thought is that there is too much voltage drop at the coils when you press the start button. Have you checked/cleaned/replaced every electrical connection and ground on the bike? If so, and you are still getting too big of a voltage loss at the coils (the closer to battery voltage, the better - no more than 1v loss), then the coil relay mod may be in order.

See this article: Diagnosing Slow Cranking

Issue 2: Have you gone through the entire air intake system to get everything tightly sealed? Have you modified the air intake system? Are you sure all of the jets and passages in the carbs are clean?

See: Air Intake Repair, Airbox Sealing, and Mikuni BS(CV) Carburetor Rebuild Tutorial

Thank you for your indulgence,

BassCliff
 
Let me ask the simple questions, how is the battery? did you try cleaning and checking the gap on the plugs? Check compression? I thought my plugs were bad after a month once and they were just carbon fouled. iI tried to clean them, but after brushing them off there was a speck of something inside the plug preventing a good spark. canned air took care of it and the bike has started every time since.
 
Since it roll starts "every time", I'd be suspicious of battery. When you hit starter button, the battery's voltage drops -sounds like yours is dropping so low that maybe igniter is not getting enough to fire plugs. Dirty connections compound the problem. You need a multimeter to check- also good time to make sure your charging system is helping out.
Having a problem with idling could mean clogged passages and/or airleak- this could also cause surging as the carbs start to function out of the idle circuit. Did you look carefully at diaphragms when you had carbs apart -sometimes pinholes occur?
 
tom203 said:
When you hit starter button, the battery's voltage drops -sounds like yours is dropping so low that maybe igniter is not getting enough to fire plugs.
Click to expand...
You are on the right track here, but I thought one point definitely needs some clarification.

The ignitor does not "need power to fire the plugs". :-k

The ignitor does not generate any kind of power to send to the sparks, it is only an electronic version of points. That's all.
It only breaks the flow of electrical current that is going through the coils. The collapsing magnetic field inside the coil is what makes the spark.
shrug2.gif


My suggestion is to check the battery capacity. One quick test is to turn the key ON and compare voltage at the battery and at the coils. Do another check while the engine is cranking. If the voltage difference between the battery and coil is more than a volt, you need to clean some connections or do the "coil relay mod". Personally, I feel that the relay mod is a Band-Aid, but it does work. Also note the battery voltage when the engine is cranking. If it drops below 11 volts, you simply might not have enough power IN THE COILS to generate a spark strong enough to fire the plugs.

.
 
Sounds like battery. I would put the battery on a low amp charger overnight to be sure it was completely charged, and be sure you have a clean ground (or two).
 
Well, I charged the battery last night, and it fired right up, repeatedly. But after a short ride it didn't want to start again. So I cleaned up the starter connections, and a few others that were close by and it started up again. Took it for a ride up to a gas station, and on the way it sputtered hard, and came through it, but after that the brake light and turn signals wouldn't work. Put gas in it since I was there, and it didn't want to start for a few tries. Let it sit for about 3 minutes and it started right up. It is now starting consistantly but my brake lights and signals still don't work. Any ideas?


The battery is at 12v, and during cranking it is at 11.2v. I'll pull the tank off tomorrow and see what the voltage is at the coils.
 
You should read up on the stator papers (go to the In the Garage section) found on the main GSResources page. I believe Basscliff also has a link to them. Run through the entire set of tests (must have a fully charged and known good battery to get good results) and see if the R/R or stator is going bad.

Good luck.
 
I'm curious what the issue is. I have a feeling it's the battery. low electrolyte, or perhaps dead cells. I replaced my battery when I first got my bike because it acted like that.
 
Your static battery voltage is too low. It should be 12.5 - 12.7 volts. This is an indication of a faulty charging system. Implementing the stator papers will give you lots of insight in this area.
I strongly suggest that you also take the battery to an auto parts store and have it load tested.
 
DrunkenChekhov said:
Well, I charged the battery last night, and it fired right up, repeatedly. But after a short ride it didn't want to start again. So I cleaned up the starter connections, and a few others that were close by and it started up again. Took it for a ride up to a gas station, and on the way it sputtered hard, and came through it, but after that the brake light and turn signals wouldn't work. Put gas in it since I was there, and it didn't want to start for a few tries. Let it sit for about 3 minutes and it started right up. It is now starting consistantly but my brake lights and signals still don't work. Any ideas?


The battery is at 12v, and during cranking it is at 11.2v. I'll pull the tank off tomorrow and see what the voltage is at the coils.
Click to expand...
A bad battery can cause alot of strange things to happen. Batteries go bad in different ways. I have seen people work and work on cars and find out it was the battery all along. I would get it tested,bike batteries arn't know for their long life. Break light and signals maybe a fuse?:)
 
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