Help! Bad bore and hone work...

CammyRacing

CammyRacing

New Member
Sep 10, 2011
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Farmington Hills, MI
As a little back-story, I bought my blaster completely torn down from a guy who was not interested in completing the rebuild. It came with everything I needed and I’ve only had to buy a couple replacement parts and some fasteners so far. The cylinder was bored and honed by a local dealer before I bought it and a wiseco piston was provided. I got it all together last weekend but I was not able to get it to start consistently and idle. I checked compression and found out it was only at 60psi. So today I checked the clearance between the piston and the cylinder wall and found out the clearance is 0.20mm. Correct me if I’m wrong, because I’m new at this, but shouldn’t it be more like 0.035mm for clearance?? So, my question is, will I have to get it re-bored for a new piston? The piston I have now is .40 over, would I just have to step up to the next size piston? Here are some pictures:

2emhif6.jpg


34pkjo6.jpg
 
Something really don't look right there.....looks off center....maybe I've just had.to many...burppppp....
 
yes....clearence.... .002 - .005, not .020
possible bum bore job

piston to cylinder clearence is measured from the bottom, with piston at BDC, between the skirts and cylinder wall

have to ask,,,,,,,,,,,

was the piston in the correct direction, and rings in correctly ???
was the compression test done with the throttle wide open ???
new head gasket ????
 
Would the large amount of clearance I have cause the low compression? The black area in the picture is gap, not shadow. It looks off center because I took the rings out to measure the clearance of the piston, should I not have done that? I had to use a feeler gauge because I do not have the tool to measure the cylinder properly.
 
mmajay said:
I would take the piston and jugg and get it measured right before you go any further.
Click to expand...

agreed, take it to a reputable shop, and not the same one that did the current work
 
Probably why he didn't finish the project. Get it measured up, might luck out and have proper bore size, but just wrong piston. If the piston is in good shape might be able to sell it.
 
The piston is brand new! I will prob sell it unless my husband can use it in his blaster. I'm guessing the shop screwed up. I have the reciept for the work and it says the piston was provided to them for the work. But I will get it checked out sometime this week.
 
Another thing to watch out for is the rings, proper size gap and make sure the gaps are not set inline. Since you have feeler gauges, you can set the ring (off the piston) in the bore, use the piston to square the ring in the bore and measure the end gap with the feeler gauge, make sure the gap isnt more than .014 for the top ring and .020 for the second.

If you have a problem finding someone to measure the jug and piston, I have the correct tools, let me know if i can help.
 
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Puma said:
Another thing to watch out for is the rings, proper size gap and make sure the gaps are not set inline. Since you have feeler gauges, you can set the ring (off the piston) in the bore, use the piston to square the ring in the bore and measure the end gap with the feeler gauge, make sure the gap isnt more than .014 for the top ring and .020 for the second.

If you have a problem finding someone to measure the jug and piston, I have the correct tools, let me know if i can help.
Click to expand...

Not possible with a 2 stroke as the piston is pegged in the ring grooves to stop ring excursion.
 
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