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The 2-Stroke Garage => Turning Wrenches => Topic started by: Striker1423 on March 08, 2022, 05:29:56 PM

Title: Top End Do-Over Questions
Post by: Striker1423 on March 08, 2022, 05:29:56 PM
I'm at the point where a side cover gasket and the electrics and ripping is ready for this motor again.

But, the top end is a bit of a concern. John corrected the squish and instructed me to buy 2 of the same sized .040 head gaskets. Of course I did that. But, the heads were marked before I installed them and once cleaned etc, I think I must have cleaned off the sharpie. So, do I need to get out a few chucks of solder and some calipers to re-check the squish on each side?

Also, when it comes to measuring pistons. I intended to measure the skirt with my calipers, and the bores of each cylinder as well.  Then install the replacement pistons where they best fit. Is this the typical way this would be done? I know bores are typically honed to match the pistons, but since I'm working on a quasi-blow-up, what should I look out for?
Title: Re: Top End Do-Over Questions
Post by: m in sc on March 08, 2022, 06:21:38 PM
what i did, similar situation, is check skirt to bore clearance in a few spots with thin brass a feeler gauge and check the best fit.  not preferred or ideal, but worked for me.

id recheck squish for sure.  :twocents:
Title: Re: Top End Do-Over Questions
Post by: Striker1423 on March 08, 2022, 09:54:39 PM
Right ok. I'll have to get some solder. The heads look the same, but I think John matched them up to specific bores.

The piston measurement I figure id get the closest hole matched up as you said and run it. John said it was such a short time on the top end it would likely still be straight.
Title: Re: Top End Do-Over Questions
Post by: soonerbillz on March 09, 2022, 08:56:02 AM
So what squish minimum are you all working off of?
I see .09mm is a minimum on various threads I've read.
How much can you realistically change a base gasket before you are messing with port timing?