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Author Topic: Piston is hitting head on new rebuild help please  (Read 7138 times)

Offline Glamisrider

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Really you need to remove the cylinder and have it measured by a pro or try it yourself if you think you ca do it right.

Ice racer should be able to guide you in the right direction as to how tall the cylinder should be from base to top deck.


Offline Stpltn250r

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think the base is ok. he said at bdc it was even with the bottom of the ex port. its just at tdc it hangs out, which like jerry said. does it have a long rod, stroker crank or wrong piston. says it doent have any of that so the top of the cyl has had to much removed. at tdc it sticks out the hole.

Offline MD2smoker

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Spend $20-$30 on a decent micrometer. You will use it many many times. I dont know what the exact # s are. But i know the factory suzuki manual will tell you the cylinder and sleeve heights. Measure them or have a pro check it. 
You said that the piston is covering the exhaust port just before TDC but at what degree on the crank rotation is that?  Without a degree wheel you cant know if the port timing is correct.
I also wonder about the PC on the cylinder.. It looks great but often PC'd cylinders need redecking afterwards due to the baking heat of the PC.  Could your builder have decked too much to compensate for the distortion of the base or head surface after the PC was cured?
Im kind of echoing others here... You need to get very specific answers from the builder to find out whats up. And take it from there.  I suspect the cylinder was far from true on either the base, head or both sides and material was removed to square it up.

Offline MD2smoker

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Sorry just saw you were saying the piston was BTDC on that.  Im not sure of what the measurement or position of the piston should be on the 250 at BTDC, but i do remember very detailed pics and measurements from my factory 90 250 manual.

Offline Rytie77

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Ok so I took some mesurements hope I did it rite my cly from the top base to the bottom base was 4.8 830  came across another cly it was 4.9 260 in  MM mine was 123.78 the other cly is 124.77

Offline Kyle T

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That's 43 thousandths of an inch, and 0.99 of a millimeter. Might as well be a mile! 0>me

Offline Rider414

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Spacer Plate or a Custom Head -
Ain't ever seen it......but I have heard it.

Offline Rytie77

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Having a plate made and hope it does the trick thanks guys for all the input

Offline Kyle T

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It will work! +k2

Offline Iceracer

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Be sure and measure the bore the head is set up for. You spacer plate will work fine to +- zero out the piston to top of cylinder. It sounds like you have a couple common issues, stock head that hasn't been chambered properly for the bore size and a sleeved cylinder. As you piston grows in over sizes you NEED to have the head opened up at some point to properly clear the piston or you can crush the ring lands. A sleeved cyli deer will have had the topof the cylinder trued to set the sleeve the same height as the casting.  If there were imperfections it could have had a lot taken off usually  a few thousandths is all you need but a bad cylinder ;can require much more.
Be sure to check the head.

Offline WestTexasKing

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 No grinder?   :'(

Offline Iceracer

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Use a Chisel... call it a turbo cut... LOL

Offline 1986QuadRacer

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A chisel? Shoot just drip a little acid down there till it works silly. It'll probably be polished too maybe.  P*

Offline James Dandy

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Re: Piston is hitting head on new rebuild help please
« Reply #63 on: September 10, 2013, 08:39:47 pm »
I joined QR just because of this post. I gotta know how it all worked out and how this thing runs!
I'm sure it's gotta run on 110 or greater, I'd say she's gonna have plenty of compression. I'm building an 88 motor right now. The faces where the cyl bolt to the case on mine are a little scarred up and I've been gathering info on how much can be cleaned off of each cyl land and what head and port mods must follow. Found a must read for everybody (since it's free) http://www.datafan.com/Horsepower_Blog/gordon-jennings-two-stroke-tuners-handbook/
Check it out! Loads of info. It's got slot of the formulas. Also I have an LT manual here if y'all want me to look anything up.

Offline James Dandy

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Re: Piston is hitting head on new rebuild help please
« Reply #64 on: September 13, 2013, 10:56:05 am »
What's the scoop on this build? Any progress?

Offline Rytie77

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Re: Piston is hitting head on new rebuild help please
« Reply #65 on: September 17, 2013, 12:37:26 pm »
some lol i had a spacer plate made fix that issue almost done had some water pump issues all new stuff still leak got a new impella  and it stoped leaking which i dont no how but it fixed it

Offline CrustyOreo

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Re: Piston is hitting head on new rebuild help please
« Reply #66 on: September 17, 2013, 02:02:39 pm »
I'm ignorant. Why did he have to make a spacer? Why couldn't an alternative solution be had? Is his Jug decked?
Read me; you'll probably regret it
http://oneguytwowheels.blogspot.com/

Offline Rider414

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Re: Piston is hitting head on new rebuild help please
« Reply #67 on: September 17, 2013, 02:18:50 pm »
His piston was sticky out of the top of the cylinder ALOT when it was put together.

We are speculating that "someone" aggressively cut the deck too much. So he had a space plate that would be placed at the base to raise the cylinder back up to spec.

 
Ain't ever seen it......but I have heard it.

Offline LT250RWV

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Re: Piston is hitting head on new rebuild help please
« Reply #68 on: September 17, 2013, 03:58:56 pm »
Now on mine I had .40 off the bottom and .20 off the deck. But I run thicker afm gasket to fix mine .I think the gasket is .40 .when I had my head cut fir proper squish I had to use a gasket because of a defect in the cylinder.
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.

 

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