Won't start after top end rebuild...Help please.

[joeak47]

I rebuilt the top end because there was a hole melted in the top of the piston because the oil ijection was bad. I bought it like that and the first thing I did was the block off kit. The only other mod is tors removal. I hooked it back up just to see if it might start like that. Also the reeds are good and carb adjustments are done according to the factory manual. 1 1/2 turns out. I'm on my way out to the garage to pull the flywheel off and check the keay to see if it's sheared. I'm almost sure this is the problem seing as I've eliminated pretty much everything else.

I doubt that the oil injection system was bad. Its a great system that gets blamed for everything that goes wrong when the engine fails. A hole was burned through the piston? THATS A LEAN CONDITION. This can be caused by many things from air leaks to improper jetting. These are the top two things I would be taking a look at.
Your engine , without question, is screaming for a leak down test. This will help you find any leaks you may have and is VERY, VERY important!. After you determine that there are no leaks, continue on to proper jetting.
What modifications have you done to your bike? What pipe are you running? What main jet are you running? What gasket set did you use? Air filter clean? What EXACTLY did you do to rebuild the top end?
Please don't get the "I've got to ride NOW" mentality without checking the items I mentioned. If you do, it could mean the difference between doing ANOTHER top end VERY soon, or enjoying your blaster for a very long time with zero issues. Hope this helps.

 

[joeak47]

I rebuilt the top end because there was a hole melted in the top of the piston because the oil ijection was bad. I bought it like that and the first thing I did was the block off kit. The only other mod is tors removal. I hooked it back up just to see if it might start like that. Also the reeds are good and carb adjustments are done according to the factory manual. 1 1/2 turns out. I'm on my way out to the garage to pull the flywheel off and check the keay to see if it's sheared. I'm almost sure this is the problem seing as I've eliminated pretty much everything else.

I doubt that the oil injection system was bad. Its a great system that gets blamed for everything that goes wrong when the engine fails. A hole was burned through the piston? THATS A LEAN CONDITION. This can be caused by many things from air leaks to improper jetting. These are the top two things I would be taking a look at.
Your engine , without question, is screaming for a leak down test. This will help you find any leaks you may have and is VERY, VERY important!. After you determine that there are no leaks, continue on to proper jetting.
What modifications have you done to your bike? What pipe are you running? What main jet are you running? What gasket set did you use? Air filter clean? What EXACTLY did you do to rebuild the top end?
Please don't get the "I've got to ride NOW" mentality without checking the items I mentioned. If you do, it could mean the difference between doing ANOTHER top end VERY soon, or enjoying your blaster for a very long time with zero issues. Hope this helps.

 

[Dutter]

There is NO WAY failed pump will burn a hole in piston?

 

[joeak47]

Nope....You have a LEAN condition. Think of it this way...
Think cutting torch... When you have the correct acetylene and oxygen mix dialed in on a cutting torch its called a neutral flame, or in another way a "Balanced air fuel ratio". This would be metaphorically the same as proper jetting in a two stroke engine. Now back to that cutting torch... When you depress the oxygen lever your adding extra oxygen which makes it an oxidizing flame, so that it can cut metal, or melt metal. This is what happened to your piston. A lean condition caused it to become oxygen rich. Where is the lean condition coming from? You need to do a leak down test BEFORE tearing your engine down. It could be anywhere. It could be a bad seal, damaged/cracked case, base gasket, exhaust gasket, rubber intake manifold, reed gasket(s), head gasket, etc , etc. After you have determined that there are no leaks with the tester and soapy water, then it comes down to jetting. More folks have fried they're two stroke engine due to IMPROPER JETTING than anything! Two stroke engines are temperature and altitude sensitive.

 

[Larry's Shee]

Joe, you quoted a 5yr old thread that was dug up

 

[joeak47]

Wow I guess I did...need more coffee. :I

 

[bansheedave]

Keep digging, I enjoy reading the replies

 

[joeak47]

There is NO WAY failed pump will burn a hole in piston?

Actually this is what brought back the old thread... /\ /\ /\

 

[joeak47]

That was from last Friday.

 

[Larry's Shee]

Nathanastone
MIA
4/17/2010​

Good info tho, Joe. Can't say someone didn't search.