Yamaha G9 running hot

[Spicyunicorn]

Very well could be a 4 mile ride with no stops will generate a lot of heat especially with a hot outside temp

[eat wake]

Took it out again for a 2 mile ride (84F outside) and the same thing happened when parked, the exhaust was crackling and smoke was coming from where the exhaust attaches to the block. I only ran it at 75% throttle, appx 14mph, and it runs really nice. I was curious if the new gasket I put on could cause this little bit of smoke? Am I still missing something that could cause overheat? Am I being too cautious? I have a video, but not sure how to upload???

[Mike Mac]

You need to remove ALL the shrouding from the motor, and clean all the caked on grease and dirt trapped in the cooling fins going all around the cylinder and head!! It's got to look like bare aluminum when you get done!! The flywheel is not the problem!!

Motor needs to look like this when your done!!

Now watch Tommy come in and complain about me stealing his picture!!......

[marks141]

We cleaned that engine really good, it's a nice running cart


Sent from my iPhone using Tapatalk

[sho305]

Bad ignitor can make them run hotter because it advances the timing at low rpm, though if you are going faster the whole time seems like it would not be an issue. Also not having much preload on your secondary will make rpm quite low at mid or low speeds and low throttle, its nice and quiet, but the fan also runs slower. That is not an issue at high speeds where it is all shifted out and revs up anyway. Any fuel issue making it lean or leaking airbox could make it lean, but you'd likely see runnability issues too. G2 can have big panels under the motor they got rid of on G9s, they close off the bottom of the cart some and make them run hotter.

If you got smoke on the head its leaking there or caked with oil, etc.

[CAMPERCART2013]

I think the crackling noise you are hearing is the oil burning out of the muffler. I also would recommend a very good cleaning of entire engine like everyone else is

[Brantley40]

I use a MyChron gauge on my G9 to measure head temp and wonder what should be a "normal" temperature or a max temperature. Anybody got a clue?

[Brantley40]

Its been running about 400-410°F, changed the carburetor to a PZ27 to try to get more out of it, was able to cool it down, but running too rich, retarded the timing on my custom ISKY smallenginecam and jetted to get the power back up and seems to stay below 400°, max rpm's I can get is about 4100, just wondering where the sweet spot is for head temp. BTW I bored the 285cc to 300cc and shaved the block for zero popup and milled the head for higher compression. No changes made to the valve size.....which seems to be my limiting factor.... Any help would be greatly appreciated on head temp numbers. Thanks!

[sho305]

The exhaust port is tiny, I would port it out if you can. Some port them through then you have to weld it back shut. There is not a lot of room there but anything helps, its a known issue the exhaust is not that great, exhaust valves go bad from heat, etc. The intake looked a lot better from what I recall, I could not get my pinky finger through the exhaust.

Running rich will cool it more, I always run rich on the main with small air cooled engines but you can't be too rich at part throttle or you get runability issues.....which is why I put a CV carb on my clone. Its working well so far but not fully dialed in. Though its a larger 32mm (stock is 24mm at most) so it feels different.

Retarding your cam, if that is what you meant, should give more rpm but it may not come on as strong. The stock timing on G9 is zero at starting and 2500 and over is full advance of 28 or something.

I never checked the head temp, guess I did have a IR temp reader then but never thought of it. Its most important to make sure the fins are clean and shrouding is fully closed up for best air flow. My rocker cover leaked and made a huge mess in mine once. You can also tighten up the secondary spring a little more and that will give more rpm at part throttle, and of course its fan cooled so that could help it cool a little better in general.