2000 G16A stalls when hot

LLESUEUR

thumbup:I purchased a used 2000 G16A with lift kit in really good condition. The purpose was for our poultry farm supervisor to use it instead of the pickup to reduce gasoline costs. Initially it was a little hard starting and required pressing only lightly on accelerator while choking. Ran great and had plenty of power until it had been run awhile and the engine warmed up. The engine cuts out as though you turned the ignition off for a few seconds. It finally gets to the point that it will cough and spit back almost like a timing issue or valve issues.

The following is a list of the things I have done so far with no results:
1. Drained the fuel tank & filled with new gasoline.
2. Removed the fuel pickup and checked the hose to verify it was clear and not collapsing.
3. Replaced the inline fuel filter
4. Replaced the spark plug with the standard NGK BPR2ES--because it was fuel fouling.
5. verified the fuel pump is working by disconnecting the fuel supply hose from the carb and placing the end in a jar. While rotating the engine with the starter the fuel was being pumped into the jar at a reasonable rate so the push pull of the engine vacuum apears to be ok.I can't really verify the push/pull is continuing or not after the engine is hot. I have two questions; Q1=If there is a seal on the engine somewhere that may be leaking? Q2=Which one is it likely to be?---Q3= Is is possible for the valve stem seals to be leaking off more pressure when the engine is hot and compromise the vacuum push/pull needed by the fuel pump?? Note: Engine does not burn any oil
6. Checked compression twice; When cold=168lbs. When hot=160lbs.
7. Cleaned the carb, all jets, checked float level adjustments, and the pilot jet adjustment. Reinstalled with new manifold gaskets--It ran the same.
8. Replaced carb later with a new one after a an unqualified friend tried to help when I was away and damaged the carb float pin and post.
9. Rechecked the one pilot adjustment screw on the new carb and found it to be set the same as the old carb (between 1.5 to 2 turns from bottom)
10. Reluctantly replaced the ignition coil unit.(TCI) The ohmic value reading for Pri & Secd read the same as the old one. Replaced it anyway because coils can be intermittant when hot.
11. When installing the new TCI I set the gap by placing a strip cut from a post card placed between between the armature and the flywheel magnet until the bolts were tightned and then removed the post card strip. I also cleaned the surface of the magnet with a scotchbright. I have three questions about this; Q1=How critical is the actual gap here??---Q2=Does the gap distance change the the spark advance here? (Close gap advances timing, Wide gap retards timing.?) Q3= If not then how is the timing advance made on the TCI in a 301 cc engine? Reason I ask this is that the G16A specs list the ignition type as a TCI with variable advance.----I see no way to advance or retard the timing unless it is accomplished by changing the gap distance.---I was taught to keep the gap between flyhweel and magneto as small as possible to provide the strongest spark voltage.---Someone please advise if the yamaha is different.
12. Replaced the sparkplug again and verified a spark at the plug tip when rotating the engine with the starter.
13. Checked valve adjustments and found clearance about .010 inch which I know now is wider than the .004 inch spec which I just learned from posts on this site.
14. My initial concern was that the clearances may have been to small which could have became no clearance when the engine was hot and possibaly causing the problem. Obviously this is not the problem however I will reset the valve clearance today to .004.
15. I have already checked all the usual electrical items such as the stop relay, accellerator stop switch, ignition switch to rule out contact bounce. I checked wiring for shorts, insulation etc. I also disconnected the two wires running from the engine to the stop relay. wiring to rule out contact bounce.

l obviously have missed something because the problem is still there so I would appreciate anyone that has answers to my questions above or may have the quick fix answer.

help: llesueur

BGW

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BeatYourTruck

Is it any better after resetting the valves to .004? Could this be a fuel / vapor locking issue? Check fuel line routing and make sure there is not one close to the muffler etc that could be causing a vapor lock issue. Any other possible fuel line issues? Ethanol is killing our rubber fuel components. Might be cheap and easy to just slap all new fuel line on. At least you could rule it out completely that way.

I think if it was a timing issue.....you would have run problems all the time, not just when hot. I still set them the same way as you did. A business card or playing card. That method has never failed! ;)

I am by no means a cart genius, just trying to get my first one ever into shape but I am an engine guy. It sounds like you are also and have done a lot of work trying to weed this one out. Keep at it....you'll figure it out!

LLESUEUR

Thanks for the reply,
Reset the valve clearances yesterday. removed the new carb and cleaned all the jets just for fun again. Put everything back together and fired it up for a short run before dark. Engine started and ran OK except it just didn't have the power or speed expected. It really feels like what you would expect when the timing is retarded on an engine. It did not skip or cut out out just ran sluggish. I didn't run it long enough to get it completely warmed up so don't know if it will begin stalling again when hot.

I previously checked all the fuel lines and the vacuum line to the fuel pump.
It is getting plenty of fuel.

Last thing I did yesterday was to remove the air filter element and the pre filter. It did run better but still acks like something is holding the cart back. Top speed is about half what it should be. I don';t think it is the governor because its adjustment has not been changed and it has run better and faster before the problems began.

I have even thought about the possibility that the woodruff key in the flywheel may have been slightly deformed which could throw the timing off---but have not checked this yet. The engine side cover is a Bear to get off to gain access to the TCI and flywheel so I may wait until a few more posts are in before revisiting that.

Mean while I may just replace all the fuel hoses and may also rip the fuel pump apart even though it was working to make sure it is not clogged.

I am still thinking ignition timing issues and hope someone out there may be aware of anything that can be affecting the timing.

Thanks for your tips,

bigstik40

Well, you certainly seem to have looked under "all the rocks" !!! After all that, It's time for a revisit of your original problem (cutting out after running a while). Is it still doing that, or is it now just running crappy with no cutting out ?? Sounds like maybe the latter ! If now just running crappy you may want to check for too rich or too lean condition by reading spark plug. Also, clutches not working properly can act like crappy running. A quick check on clutch operation while in neutral would be in order. The clutches both need to have a shot of grease from time to time to keep them articulating properly. Let us know what you find. RAY

LLESUEUR

Hello All,
I just wanted to provide follow up information after discovering the real cause of the trouble with my 2000 G16A engine stalling and running at about half power.- See my original post for the problem and all the previous unsuccessfull troubleshooting efforts.---
Bottom line cause was that the ignition coil was defective causing the intermittent stalling and pour performance.

The reason the problem did not immediately go away after replacing the ignition coil is because the carburator had been replaced with a new after market carburator (which had a "China" manufacturing defect) prior to the coil change. The defective carb caused the cart to continue to run at about half power and speed although the hot/stalling did stop after the coil was replaced.
After being informed by a friend about past issues with china manufactured aftermarket carburators I installed an original Yamaha OEM carburator made in Japan and the old cart now has more power and speed than my newer Gmax ever had.

The total cause of the original stalling & low power issues when hot was the failing ignition coil. The only reason the carb was changed during the process was due to my employee who decided to mess with the carburator and broke the float pin post necessitating its replacement. Had the coil been replaced first the problem would have been solved and it would have been apparent.

Thank each of you that offered replys with possible solutions. I hope this follow up helps the next person with a coil issue. LL

Mike Mac

LLE, not bashing here in any way but, this is a perfect example of why I don't want parts that aren't genuine Yamaha factory parts. You can get into real expensive trouble buying brand X. When I purchase parts, I always tell or ask for the good stuff, not junk. This cost you alot of time and money.

Back a 150 yrs. ago, I bought a new brake drum for my sandrail. Put it on and went riding out in the desert. Well, it blew up in many pieces leaving me spinning around in circles less than a mile later! When I took the pieces back the next day and asked the parts guy what we were gonna do? He said he didn't know I wanted factory parts!! DUH! From there on out, I decided I needed to make sure what I was buying! (If I wanted ta stay alive for the next 149)!!