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Post by 808ministroke on Oct 12, 2021 2:38:22 GMT -5
![]()   OK so sad story the Small screw that came loose that was holding Reed did not get rinsed out when I took off cylinder or burn up like I thought... my question is with cylinder still good and scootertuning.ca not having the 13mm wrist pin version in stock could I get by with this similar 2fast piston? aND if that is a bad idea and have to order direct from malossi should I get a b size ? Bore has been through alot, 3 headgaskets blown , New head, piston ring stuck in groove which I had fixed earlier does all that plus  say like 400 500 miles warrant a b size ? compression was seeming low before any way please chime in soon before I order irresponsible educated guessing ... |
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Post by 190mech on Oct 12, 2021 3:52:40 GMT -5
Before buying,get some measurements from your old piston and try to find a match,,top edge of piston crown to top edge of pin hole will be the most important,ring locating pin location,and exact piston and cylinder bore diameters too..Post them here so we can look also..Emailing scootertuning the dimensions would allow them to look too..
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Post by repherence2 on Oct 12, 2021 10:11:50 GMT -5
808ministroke maybe time to invest in a new bore kit after reading the list of what that bore has been through.
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Post by 90GTVert on Oct 12, 2021 10:17:50 GMT -5
Mileage doesn't accurately tell you whether you need an oversized piston. Precise measurements are the only way to know for sure. Here's an example from measuring my TPR 86cc kit, with drawings up top to show where measurements were taken. I used a micrometer and a dial bore gauge. The measurements allow you to see clearances and that's how you determine the need for oversized pistons.  |
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Post by 808ministroke on Oct 12, 2021 14:30:13 GMT -5
Mileage doesn't accurately tell you whether you need an oversized piston. Precise measurements are the only way to know for sure. Here's an example from measuring my TPR 86cc kit, with drawings up top to show where measurements were taken. I used a micrometer and a dial bore gauge. The measurements allow you to see clearances and that's how you determine the need for oversized pistons. so would you not buy a oversized piston if a normal one worked fine? I was thinking I'd be able to just use a hone to open it up if needed. |
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Post by 90GTVert on Oct 12, 2021 17:16:40 GMT -5
You shouldn't be honing to create clearance, especially with a coated cylinder. You would be much better off to clean and inspect the cylinder. If it's in suitable condition to reuse, measure it. If you think it needs some sort of touch up, do that and then clean and measure again. If the coating is bad, then replace the cylinder kit or you'll have to get it re-plated. Re-plating and a piston are likely more than just getting a new kit.
I was seeing roughly 0.0025" with a new cylinder and piston on the TPR 86cc. I'd expect that or even up to 0.0035" to be a good target for the MHR 86cc as well. I noticed no difference a couple thousandths over TBH. Pistons should be wearing more quickly than the bore/coating, so a new A piston may be all you need to get acceptable clearances.
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Post by 808ministroke on Oct 14, 2021 1:50:49 GMT -5
I take your word on just about anything Brent, especially when I have come to similar conclusion.
I inspected it thoroughly and can only see super slight scuffing before Tran ports not nearly as bad as my ex. bridge both are so minor they cannot be felt in any way. have to give Malossi credit they made a nearly indestructible 3mm plating.
I have gone and ordered piston Direct from them besides them being the only people that had it I ordered a ordered A series When it seems like they offered 0 A B C Sizes I always thought that a was the original size thoughI looked on a few other sites to see if I could find it anywhere else and what I did find was some ATV sites were selling the too fast piston and displaying it as a replacement for the melosi or vice versaWas tempted to order the too fast from sc.Ca But figured it would not be wise as even though they both look exactly the same maybe the ring pin is in a different spot or something however think however if I was unable to find the exact replacement I would've went with that especially becauyet especially because it would've gotten here probably a week quicker.
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say like 400 500 miles warrant a b size ? 
