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Author Topic: Piston is hitting head on new rebuild help please  (Read 8555 times)

Offline Rytie77

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Piston is hitting head on new rebuild help please
« on: June 18, 2013, 01:41:50 pm »
Hi iam new hear I just had my motor redone I get it home and start putting everthing back together I put the kick start push down on it and goes up and stops in pull head and it moves up and down put head on no nuts and the piston hits head can I run to base gaskets and what will that change thank u

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Offline MotorGeek - Jerry Hall

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Hi iam new hear I just had my motor redone I get it home and start putting everthing back together I put the kick start push down on it and goes up and stops in pull head and it moves up and down put head on no nuts and the piston hits head can I run to base gaskets and what will that change thank u

There is a reason why the piston is hitting the head.  Do not just start stacking gaskets to stop the piston from hitting the head.  There may be other problems.

Did  you talk to the guy that rebuilt the engine?

Was the head milled?

Do you have the wrong piston?

Was the connecting rod changed?

Was the cylinder base or head gasket surface machined?

Did you bore the cylinder?  If so how much was it over-bored?

Offline Motoman991

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^^^Mr Hall covered everything.

Offline Dezsled

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With each question Jerry asked, it points to different aspects of the engine to look into. So if you can help him pin it down you'll be riding again a lot sooner

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Offline Rytie77

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Thank u for responding ok has a new hod rod crank was bored over not sure how much and not sure if it was milled I called the guy who built it and no call back but I put piston all the way down in the stroke and it looks like its perfectly level with the exhaust port

Offline MotorGeek - Jerry Hall

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Thank u for responding ok has a new hod rod crank was bored over not sure how much and not sure if it was milled I called the guy who built it and no call back but I put piston all the way down in the stroke and it looks like its perfectly level with the exhaust port

Does the edge of the piston rise above the top of the cylinder when the piston is at top dead center?  If so, is the hole in the head gasket large enough for the piston?

If the piston will go through the head gasket is the step in the head at the outside of the squish band larger than the piston?

Offline Rytie77

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It does not hit gaskit the edge of piston comes out of the cly a little but then drops back in the cly

Offline LT250RWV

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Get us some pic so we can see what your talking about.Pics help us help you.
91 Lt250r Bartlett port and head mod v force 2 Hinson Clutch Basket Cool Head Scp Pipe and silencer ,KN air filter ,EBC clutch, Ohlins  Triple rate Shocks Redone by PEP Shocks,Stock Rear Shock Redone By Pep Shock,  DG nerf Bars , Lonestar axle 2+2,Lonestar Swingarm ,Douglas Red Label rims.

Offline Stpltn250r

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get some calipers and measure the bore of the dome and the bore of the cylinder.

Offline Rytie77

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The piston pots out of the cly then drops below

Offline MotorGeek - Jerry Hall

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What is the piston size?  What is the number on top of the piston?

Offline Rider414

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Nice looking Jug -  O0
Ain't ever seen it......but I have heard it.

Offline Dezsled

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The finish on those cases looks killer too
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Offline Rytie77

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Piston number 9328e.  Top number bottom 571m06850

Offline Rytie77

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Thanks guys have a lot of time in this thing hope to have it running soon here is the hole quad

Offline Stpltn250r

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you could measure from BDCto the top of the sleeve. i bet the cyl has been milled way to much on the top. did you pc the cylinder? looks like a custom dome is in order. from my cell phone the piston looks to be out the hole by .060. thats alot!

Offline MD2smoker

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On a good note, that chassis looks awesome!  Cant wait to see this completed!

Offline Rytie77

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Thanks hope it will be done soon yes it is pc hole quad is pc the motor is holding me up were would one get a custom dome

Offline Stpltn250r

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now im on a computer and it doesnt stick out as much as i thought. the liner was making me think it was sticking out further than what it is. do you have an oem head or do you have a pro design?

Offline Rytie77

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I do not will a pro design
Help or i can try to find a head

Offline WestTexasKing

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The first picture appears to show the piston sitting above the sleeve, I've looked at it numerous times trying to see if it was just an optical trick, but I think that's where your problem is.
Try this....
-Get some thick grease and smear it thinly all over the top of the piston (make sure you get all the way to the very edge of the piston!).
-Install head with gasket and snug the nuts down (don't torque).
-Bring the piston up until it hits the head.
-Remove head and observe where the grease was left (or where the grease was squished off the piston), this will tell you where the piston is hitting and can give us more info to diagnose your problem.
-Take a picture of any findings and post here, then wipe the grease off to prevent spark plug fouling later on.

One of the things it will tell us is if the piston is hitting the head or the head gasket, another thing it will tell us is if the head itself is cut correctly or not (well, partially anyway).

Offline Rytie77

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Ok I will do that when I get home I did throw a another base gasket on just to see if it would help with the head just siting it didn't I tighted it down and it would just hit

Offline Glamisrider

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Rytie,
There should be a number 86mm through 89.5mm on the top of the piston, what is that number?
I assume this is a weisco?

Also what is the max diameter of the head gasket your using in MM (use digital calipers $10 a Harbor Freight).

If the pics shown are TDC it does not look like your piston is coming too far out, could just be the head, has it been modified or is it stock?

Offline Rytie77

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This is what's on top Piston number 9328e.  Top number bottom 571m06850
I bought it like this but had it bored and new piston I didt ask them to modified it at all

Offline Dezsled

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The last 5 digits tell you the size ... 08650 = 86.5 mm
87 HPR LT500
04 Roll LOBO II TRX250R
06 LTR450
87 LT500
85 & 86 LT250
86 & 87 TRX250R
07 & 09 Husqvarna TE450
00 CR125R

 

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