Checking "Ring End Gap" Yamaha G16

ace_ripper · 06-19-2010, 07:28 PM

Back again...

I have a strange cart here. The serial # tells me it's a G11 yet the engine block has the 'JN6 301cm3'. I'm guessing it's a crossover model or some such.

It was smoking like a freight train once warm so I tore it apart to put new rings in it. I ordered standard rings for a G16 (78mm bore). Honed out the cyclinder nicely and cleaned everything up. Installed the new rings with proper gap spacing. Buttoned it all up with proper torque specs and went for a test drive. It was still smoking...

I yanked it out and slapped it back on the bench. Tore it all back down to make sure I didn't do something stupid in the first go around. When I put the rings into the cyclinder one at a time to check to make sure these were the correct set I find that the ring end gap is about 1.021mm.

The specs show that it should be .2 ~ .4mm. A difference of .721mm seems huge to me. There are no markings on the piston as if someone had already bored it over .25~.50mm. Could this be an over sized piston without any marking on it? Should I attempt to go with a .50mm o/s ring set to try to get rid of the smoking issue?

Any help would be greatly appriciated.

Here are a couple links to sites I used for specs and proper ring setup.
http://www.wiseco.com/PDFs/Manuals/RingEndGap.pdf
http://www.golfcartcare.com/Merchant...y_Code=spaceng

ace_ripper · 06-23-2010, 04:41 PM

I had to say #@*# it and have it bored out to +.25

Will update the thread once it's back from the machine shop.

smallblock450sl · 06-23-2010, 06:51 PM

Quote:

Originally Posted by ace_ripper

I had to say #@*# it and have it bored out to +.25

Will update the thread once it's back from the machine shop.

Probably the best idea. G16 service manual calls for (top ring-std-0.04 to 0.80mm and limit is 0.10mm, second ring-std 0.03 to 0.07mm and limit is 0.09mm) Good luck on your rebuild.

smallblock450sl · 06-30-2010, 07:35 PM

So what happened today?

ace_ripper · 07-01-2010, 01:44 PM

I got the block back yesterday. With a .25 bore and matching piston/rings. The ring end gap is now .3mm. Right dead on the Yamaha specs. Got everything back together and in the cart. It runs GREAT now! No smoke, no issues what so ever. It fires up right away every time no choke needed even when cold.

My compression tester crapped out on me so no idea what the new readings are. I guess that's what you get for a $10 harbor freight special.

Thanks again for all your help.

06-19-2010, 07:28 PM	#1
ace_ripper Not Yet Wild Join Date: Apr 2010 Location: Bothell Washington About 20 miles north of Seattle Posts: 68	Checking "Ring End Gap" Yamaha G16 Back again... I have a strange cart here. The serial # tells me it's a G11 yet the engine block has the 'JN6 301cm3'. I'm guessing it's a crossover model or some such. It was smoking like a freight train once warm so I tore it apart to put new rings in it. I ordered standard rings for a G16 (78mm bore). Honed out the cyclinder nicely and cleaned everything up. Installed the new rings with proper gap spacing. Buttoned it all up with proper torque specs and went for a test drive. It was still smoking... I yanked it out and slapped it back on the bench. Tore it all back down to make sure I didn't do something stupid in the first go around. When I put the rings into the cyclinder one at a time to check to make sure these were the correct set I find that the ring end gap is about 1.021mm. The specs show that it should be .2 ~ .4mm. A difference of .721mm seems huge to me. There are no markings on the piston as if someone had already bored it over .25~.50mm. Could this be an over sized piston without any marking on it? Should I attempt to go with a .50mm o/s ring set to try to get rid of the smoking issue? Any help would be greatly appriciated. Here are a couple links to sites I used for specs and proper ring setup. http://www.wiseco.com/PDFs/Manuals/RingEndGap.pdf http://www.golfcartcare.com/Merchant...y_Code=spaceng

06-23-2010, 04:41 PM	#2
ace_ripper Not Yet Wild Join Date: Apr 2010 Location: Bothell Washington About 20 miles north of Seattle Posts: 68	Re: Checking "Ring End Gap" Yamaha G16 I had to say #@*# it and have it bored out to +.25 Will update the thread once it's back from the machine shop.

06-30-2010, 07:35 PM	#4
smallblock450sl Sometime's............ Join Date: Oct 2007 Location: Tacoma Washington Posts: 11,874	Re: Checking "Ring End Gap" Yamaha G16 So what happened today?

07-01-2010, 01:44 PM	#5
ace_ripper Not Yet Wild Join Date: Apr 2010 Location: Bothell Washington About 20 miles north of Seattle Posts: 68	Re: Checking "Ring End Gap" Yamaha G16 I got the block back yesterday. With a .25 bore and matching piston/rings. The ring end gap is now .3mm. Right dead on the Yamaha specs. Got everything back together and in the cart. It runs GREAT now! No smoke, no issues what so ever. It fires up right away every time no choke needed even when cold. My compression tester crapped out on me so no idea what the new readings are. I guess that's what you get for a $10 harbor freight special. Thanks again for all your help.

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