Scooterotica

Anybody know of who stocks oversize GT200 pistons ,I am at 66.5 (2nd oversize) need a piston at 3rd oversize (66.75) have got 4th oversize (67.0) but that has a slightly different crown height and will now cause me a headache if i use this ,so just putting feelers out

I presume you have tried Richard taylor ? I think they are a Yamaha piston, maybe banshee ?

I checked this information again. According to Mitaka/Grampian data the DT175K piston has the same compression heights as the 350LC piston. The dome height is 1.5mm higher but that isn't the end of the world. Over-sizes for this piston will take you to 67.5mm as I understand.

also checked the DT175K compared to the RD350YPVS (piston used on original GT200's) on the TKRJ manual. This states a 0.5mm lower crown height on the DT175K piston. This would increase the port timings a little, if you send me port heights I can calculate what the effect would be or you could use sealant in place of a base gasket to recover approximately 0.4mm in timing.

Rich_T wrote: ↑Sat Dec 14, 2019 9:51 pm also checked the DT175K compared to the RD350YPVS (piston used on original GT200's) on the TKRJ manual. This states a 0.5mm lower crown height on the DT175K piston. This would increase the port timings a little, if you send me port heights I can calculate what the effect would be or you could use sealant in place of a base gasket to recover approximately 0.4mm in timing.

I seem to remember that it was a common conversion for lc350 64mm to go to dt pistons as original oversize was quite small, the dt was 66mm and bigger but as you say compression height was lower and the base of the barrel had to be skimmed to get the port timings, seem to think its was about 6mm that was removed, ive got 66,25 pistons in my yambretta using mitaka pistons, they go to bigger oversizes than original Yamaha pistons.

correction ive got 66mm in mine

ive just checked and pjme do mitaka pistons in plus 2.25 and plus 2.5 think that's what you need if they have them in stock

holty wrote: ↑Sat Dec 14, 2019 7:45 pm I presume you have tried Richard taylor ? I think they are a Yamaha piston, maybe banshee ?

Yep talked to Richard,he has given me the info as below , was hoping someone may have the third o/size piston at 66.75

Rich_T wrote: ↑Sat Dec 14, 2019 8:43 pm I checked this information again. According to Mitaka/Grampian data the DT175K piston has the same compression heights as the 350LC piston. The dome height is 1.5mm higher but that isn't the end of the world. Over-sizes for this piston will take you to 67.5mm as I understand.

Thanks Richard

Rich_T wrote: ↑Sat Dec 14, 2019 9:51 pm also checked the DT175K compared to the RD350YPVS (piston used on original GT200's) on the TKRJ manual. This states a 0.5mm lower crown height on the DT175K piston. This would increase the port timings a little, if you send me port heights I can calculate what the effect would be or you could use sealant in place of a base gasket to recover approximately 0.4mm in timing.

Thanks Richard ,always very helpful. was looking to see if there is a 66.75 piston same as the RD350 one .there is a difference in crown height ,difficult to measure ,rack of eye is between 1.0mm and 0.5mm.
dont want to rebore to 67.0mm just yet