Boygofast 47mm sleeved cylinder info



Will'smotobikes19

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Apr 9, 2018
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The piston seems to have some wear has some scratching and looks shiny. Chinesium pistons in steel probably not a good match though. Maybe a forged piston along with those better rings would be a good combo.
 

HumanPerson

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Mar 4, 2017
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That piston was in the old cylinder previously, it's actually been in the klunker engine for a year.
They were new rings just used the old cylnder piston.

Today i put on the new cylinder with a new piston and new rings.

Everything seems to be working very well so far.
I was cruising at 30mph then went to the park and cruised @ 18mph then back up to 28mph
for another 40 minutes.

I guess when it gets warm and i can ride it straight for 20 miles we'll see then on the long hauls?

Ride Safe! :)


HP
 
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Will'smotobikes19

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I want to test my sleeved cylinder too its a cast iron 48mm bore with a windowed piston and reed valve. Mz miami sells them but the sleeve isn't as thick as the bgf. I think I finally got my jetting right on the mikuni vm18 #90 main and 22.5 pilot. In my car it says I'm about 3,000 ft in altitude but not sure it is a 15 year old car so it could be wonky, like my gas gauge. Tuning stuff is a pain though. I will probably use a different bottom end though as the one it's on was a cheap black engine kit with 6mm mounting studs. I'm thinking about using a stroker crank with the sleeved cylinder and I made a spacer for it a while back. I think it would be like 74cc with 48mm bore and 41mm stroke? not sure on that but I've heard the 3mm stroker crank only adds 1 mm to the stroke. With 48mm bore and 38mm stroke its still only 68cc so basically like one of the 40mm motors only 1mm bigger bore.
 
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Spare_Parts

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Nov 29, 2017
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@Street Ryderz I would like to see what he thinks about that wear pattern. Looks like there is some scoring to me.

Ordered 47x2 Caber rings off of egay. No info other than size but they are cheap enough. Hopefully they have a part number. Also found some poloni (sp?) rings but again, no info. Still searching. Now I'm using Google for other countries.
 

Street Ryderz

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Oct 14, 2016
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@Street Ryderz I would like to see what he thinks about that wear pattern. Looks like there is some scoring to me.

Ordered 47x2 Caber rings off of egay. No info other than size but they are cheap enough. Hopefully they have a part number. Also found some poloni (sp?) rings but again, no info. Still searching. Now I'm using Google for other countries.
Looks like the sleeve has some dimples/riples in the bore,would be interesting to see what a micrometer showed.
 
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