G1 head vs. Enticer head, Phazer Piston?

[Reeves Racing]

Hey yall,

I have a Yamaha G1 that was running good, but I wanted more bottom end power. I did some quick research (too quick I'm now finding out) and went with the Enticer 250 top end. Well, it runs, but it's all top end, and made the bottom end way worse. Not what I was looking for.

So now I plan to go back to the old 215 (stock) top end. I was going to do a tad bit of port work (clean up mostly) and shave the head. I've read that the Enticer head is better on the G1, but I don't understand how. It has a bigger combustion chamber (dome). How does that help? I'm just trying to decide which head to use and shave.

How much would I shave either head?

I've also read on here that a 84-98 Yamaha Phazer piston can be used if you bore the stock G1 jug. The sleeve is very thick, so this seems promising. The piston looks to be the same, other than the OD. Has anyone done this and did it shift the rpm band at all? I'd like more power but with in the stockish rpm range (unlike the Enticer 250 setup).

This is the piston kit I was looking at getting:
https://www.ebay.com/itm/234654211825


Thanks,
James

[slonomo]

G1 was made to be low compression and low rpm, so power comes in low in rpm range. STock I think it makes all of about 7hp. You might be able to get a few more say 9hp with some tweaking, and keep it low in rpm range. You won't be able to get big power gains with that jug.

The Enticer head will raise compression. It also has a tighter "squish band" built into the head, that raised dome. You find that on higher performance 2 strokes. If you shave the Enticer head and use it on the 215 cylinder you will get better performance, but again, not big power.

The stock G1 exhaust is pretty restrictive. I switched to a Plowman's muffler on mine and felt a decent gain from that and a jet change. Don Plowman has messed with the G1 for years, and he's an old school sled and dirtbike guy too so he's familiar. Might give him a call, he's in the sponsors page.

What carb were you using with the Enticer setup? I got mine to run pretty good with a Keihin 32mm, but I know if I had used a Mikuni I could have done better, maybe a 28mm would be better for throttle response off idle.

On the Enticer setup you will need a good clutch, what clutch are you using? I think an adjustable roller clutch would be best if you could find one that fits. I never made it that far with mine. A roller clutch with a 2500 engagement and 4000 full shift would be perfect for the Enticer setup. That Enticer setup would rev to over 7k rpm, it was a screamer.

I feel you on the low end power though, that's exactly why I got away from the G1/Enticer engine. I went 4 stroke, solved all my problems.

[Field6565]

Originally Posted by slonomo

What carb were you using with the Enticer setup? I got mine to run pretty good with a Keihin 32mm, but I know if I had used a Mikuni I could have done better, maybe a 28mm would be better for throttle response off idle.

I agree...28 or 30mm Mikuni slide carb would be the perfect set up for this mod. My carb was also too big and killed low end. Live and learn I guess.

[Reeves Racing]

Update: I tried several combinations and ended up with the 250cc Phazer piston from Wiseco, stock jug bored out, and stock head.

Mods: Shaved off some of the bottom of the piston so it matched the stock piston. I was afraid the bottom might be too long and hit crank. Not 100% sure this mod was needed.

I had the Enticer head on there, but was having a problem with the engine dieseling and thought it might have too much compression, so I put the stock head back on. This helped with the dieseling, but did not cure it. Ended up my crank seals were leaking. New ones fixed the issue. I could try the Enticer head once again.

I'm using the stock carb. I had bought a chinese stock replacement carb from Amazon, but the needle/seat leaked under fuel pump pressure.....so I just stole the jets and emulsion tube from the new carb. It was too lean, so I purchased a set of micro drill bits from Harbor Frieght and carefully opened up the stock jets until it ran good.

The old G1 definitely has more bottom end now. I'm curious if a Plowman muffler would help next. I had a Banshee expansion chamber on it but as we use the cart more and more I needed it to be quieter, so I purchased a used stock muffler and put it on.

[mikeasis]

Originally Posted by Reeves Racing

Update: I tried several combinations and ended up with the 250cc Phazer piston from Wiseco, stock jug bored out, and stock head.

Mods: Shaved off some of the bottom of the piston so it matched the stock piston. I was afraid the bottom might be too long and hit crank. Not 100% sure this mod was needed.

I had the Enticer head on there, but was having a problem with the engine dieseling and thought it might have too much compression, so I put the stock head back on. This helped with the dieseling, but did not cure it. Ended up my crank seals were leaking. New ones fixed the issue. I could try the Enticer head once again.

I'm using the stock carb. I had bought a chinese stock replacement carb from Amazon, but the needle/seat leaked under fuel pump pressure.....so I just stole the jets and emulsion tube from the new carb. It was too lean, so I purchased a set of micro drill bits from Harbor Frieght and carefully opened up the stock jets until it ran good.

The old G1 definitely has more bottom end now. I'm curious if a Plowman muffler would help next. I had a Banshee expansion chamber on it but as we use the cart more and more I needed it to be quieter, so I purchased a used stock muffler and put it on.

Yes the plowmans pipe definitely flows better than stock but it is more pingy sounding like dirt bike. If compression needs to come down I’d try using an 82 J17 head as it has a larger chamber

[mikeasis]

Originally Posted by Reeves Racing

Update: I tried several combinations and ended up with the 250cc Phazer piston from Wiseco, stock jug bored out, and stock head.

Mods: Shaved off some of the bottom of the piston so it matched the stock piston. I was afraid the bottom might be too long and hit crank. Not 100% sure this mod was needed.

I had the Enticer head on there, but was having a problem with the engine dieseling and thought it might have too much compression, so I put the stock head back on. This helped with the dieseling, but did not cure it. Ended up my crank seals were leaking. New ones fixed the issue. I could try the Enticer head once again.

I'm using the stock carb. I had bought a chinese stock replacement carb from Amazon, but the needle/seat leaked under fuel pump pressure.....so I just stole the jets and emulsion tube from the new carb. It was too lean, so I purchased a set of micro drill bits from Harbor Frieght and carefully opened up the stock jets until it ran good.

The old G1 definitely has more bottom end now. I'm curious if a Plowman muffler would help next. I had a Banshee expansion chamber on it but as we use the cart more and more I needed it to be quieter, so I purchased a used stock muffler and put it on.

What year range Phazer piston did you use? Did you have to sleeve the cylinder

[Reeves Racing]

I used a 84-93 73mm Phazer piston from Wiseco that I purchased on eBay. Just bored the stock jug.

[mikeasis]

I would think the sleeve is pretty thin at that point
There’s a lot of meat in the G1 cylinder but going 5mm over is a lot

[Reeves Racing]

Still enough meat and runs great. The jug casting for the Enticer is also 73mm and is the same casting.