Bike ran fine, now BARELY running. Help please?

Re-timed the bike. Left side was a little off, right side was spot on. Rode it down the road again, and its still doing the sputtering thing. Had it in 6th gear pinned and was only doing 60mph. Looked at the spark plugs, left side was black and a little wet, right side was like tan/white and dry
 
Did a compression test and both checked in at 100psi. I know that's low, but could that be an explanation of why my spark plugs are so different after I run it?
 
AaronKyle432 said:
Did a compression test and both checked in at 100psi. I know that's low, but could that be an explanation of why my spark plugs are so different after I run it?
Click to expand...

Are you kicking it over or using the electric start to do the test? How many kicks per test are you doing or how long are you cranking the starter? Did you do a wet compression test yet?

No, the low compression wouldn't account for the difference in plug color especially since both sides are testing the same. The tan plug actually looks pretty decent. The dark one is obviously fouling out on you. Have you checked the carb diaphragm on the dark side?

Did you look at the coil on the dark side? Look for any leaking tan goo coming out of it. You could try swapping coils from side to side to see if the problem changes sides. I am pretty sure you can do this without removing the coil from the bike; you just swap the plug caps (assuming they reach) and red/orange wires (If I remember correctly).
 
If a wet test for compression brings the numbers up then it's time for at least rings and a hone.
 
When doing the compression test, I did a dry test and used the electric starter, turning it over about 5 or 6 times. I borrow the compression tool, so I didn't try the wet test to see if the rings were bad. I'll see if I can borrow it tomorrow and try it.

I looked at my coils when I did my timing, but I didn't notice anything out of the ordinary. I'll try switching the plug wires to see if they burn differently. Im about to just take it to a shop and have them diagnose the problem because I'm almost out of ideas.
 
Unless you can find a shop with an older mechanic, I would suggest not wasting your time or money. Every mechanic I've met under the age of 40 is nothing more than a "parts replacer". They stopped teaching common sense at trade schools a long time ago...
 
If you have a yamaha dealer near you go there. They should only have certified yamaha mechanics working there that can work on all bikes, at least mine has:shrug:
 
I guess it is a different market here. All dealers I've been to in Southern Ontario, regardless of make, haven't been interested in working on "old" bikes. They consider a bike "old" after 7 years. I've even been told to go to independent motorcycle repair shops because the "technicians" (not Mechanics!) don't have the training or experience working on "old" bikes, and they have no parts in stock. They don't want to have a bike in their shop taking up space for a week while waiting for parts...
 
Over time and also from sitting rings can be stuck in the pistons causing low compression.
 
The engine starts and isles fine completely cold. It will sit there and idle all day, but if I try and ride it and get it into 2nd or 3rd gear (or put any strain on the engine with higher RPM's), the bike doesn't want to idle after I do that. Going to the shop Wednesday to hopefully find the culprit
 
It sounds like you really may have low compression. If it's consistent and equal on both sides whatever rings/pistons are in there just aren't making a good seal. Again, I think you could do a wet compression test to confirm this before taking it to a shop.

xschris said:
Over time and also from sitting rings can be stuck in the pistons causing low compression.
Click to expand...

This happened to mine. The carbon and junk caused one of my rings to stick in the fully compressed position.
 
Re-checked compression tonight and did a wet test. 140psi left side, 150psi right side on the dry test. 1850psi left side, 200psi right side on wet test. So, I dont think the rings is the culprit on why it's running bad under pressure. The carbs have been cleaned and timing has been set and pistons seem good. So, what could possibly be the problem? Ignition problems? Ignition gapping or wires bad? Maybe I didn't clean the carbs very well? Like I said, it's cutting out around mid-range and top end is very very weak. Idles fine before I take off, then once I try and ride it while it's barely going, it doesn't want to idle after that
 
Are you absolutely certain the timing is set right? How much experience do you have in this area? I have absolutely screwed it up before myself.

The other suspect I have is the coils. In my experience when they went bad the bike would run initially and idle ok when it was cold. After riding for a short distance things heat up and the bike would die.

Cables? Probably not; it would run crappy all the time, not just when warm. They also tend not to go bad. If there is a bad connection on the cap end you just trim a little off and re-screw the cable back in.

Carbs? If it initially idles ok it should idle ok after it's warm and ridden. Now, if the problem was consistent I would suspect them. For example, if the bike idles fine, but had no top end. Since you're saying the bike doesn't want to start/idle once it's warm I think carbs are not high on the list.

Ignition gap? Again, probably not because this is a constant and your problem seems to be related to temperature.
 
Don't know if it has been mentioned before, but have you checked for air leaks in the intake? Exhaust gaskets? Sometimes we overlook the simple stuff.
 

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