Deuczwild Posted June 12, 2015 Report Share Posted June 12, 2015 Hi, first off want to say awesome site, gave me a lot of info on some different things. Recently bought a banshee, had some problems, boiled down to having 90 psi on both, want to do rebuild but not sure what size motor I have. I know its power valve cheetah. But not sure what size? On top of my dome it says cheetah 68.5 - 21 - 10. Any and all info would be surely appreciated. Thanks Quote Link to comment Share on other sites More sharing options...
BANSHEE HP Posted June 12, 2015 Report Share Posted June 12, 2015 68.5mm bore, 21cc dome with 10* squish angle. i supposed it could be a stock stroke or 4mm... even 7mm but 4mm is the most common option. 1 Quote Link to comment Share on other sites More sharing options...
Deuczwild Posted June 18, 2015 Author Report Share Posted June 18, 2015 I believe its a stock 54mm stroke when I tear into it ill know for sure. Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted June 18, 2015 Report Share Posted June 18, 2015 You can take a spark plug out and hand crank the motor to tdc. Insert a pencil and mark the pencil when piston is at tdc. Then hand crank motor to BDC, mark pencil again. Measure distance between both marks and if it equals 54mm or 2.126" it's stock stroke. 4mil stroker >> 58mm or ~2.283" 7mil stroker >> 61mm or ~2.402" 10mil stroker >> 64mm or ~2.520" Quote Link to comment Share on other sites More sharing options...
Deuczwild Posted June 18, 2015 Author Report Share Posted June 18, 2015 yea I did that and it measured round 5.4 cm which would be 54mm but I still have to tear it apart regardless. Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted June 19, 2015 Report Share Posted June 19, 2015 Yup, you sure do. The bore is 6.85cm and the stroke is 5.4cm. Then displacement = bore x stroke or 398cc's. Quote Link to comment Share on other sites More sharing options...
Deuczwild Posted June 19, 2015 Author Report Share Posted June 19, 2015 Yea that's what I been reading I figured it was bout a 392 or something with the 68.5mm bore and 54mm stroke the guy I bought it from thought it was a 421 but after doing some reading I think its a 392 or something which is bout right. Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted June 19, 2015 Report Share Posted June 19, 2015 6.8cm bore and 5.4cm stroke is 392cc's. 6.85cm bore and 5.4cm stroke is 398cc's. 6.8cm bore and 5.8cm stroke is 421cc's. Quote Link to comment Share on other sites More sharing options...
Deuczwild Posted June 19, 2015 Author Report Share Posted June 19, 2015 awesome thanks, now I just have to find a couple of pistons to rebuild and then ill be able to fly round the trails. Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted June 19, 2015 Report Share Posted June 19, 2015 If I were you, I'd send the whole motor into someone like Redline Racing or FAST. Find a site sponsor that specializes in Power Valve Cheetah Motors and have them inspect and blueprint everything. With an engine build, a sponsor would probably charge you $250-$300 to do a complete tear down and reassembly and leak check for you. This would give you the piece of mind of a solid built motor that you can drop straight back into your frame and be ready to go riding in a weekend. Maintenance, maintenance, maintenance... Is key to reliability and longevity. Or, if you have the skill and the know how, send in the crank, the cylinder, domes, top case and have it transfer port matched and the transmission and have it ProMod cut. Get a Clymer Manual if you don't have one already. Buy a FAST Carb Sync Tool and learn how to sync and tune your carbs. Now I'm not sure about Nikasil'd cylinders and how they wear or if they wear, so leave the inspection to the sponsor. There's so much more to say... Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted June 19, 2015 Report Share Posted June 19, 2015 This is an awesome read about power valve cheetahs. http://bansheehq.com/forums/index.php?/topic/155869-421-cheetah-pv-vs-421cub/?hl=cheetah Quote Link to comment Share on other sites More sharing options...
lil Doobie420 Posted June 19, 2015 Report Share Posted June 19, 2015 (edited) Trial and error ftw Edited June 19, 2015 by lil Doobie420 Quote Link to comment Share on other sites More sharing options...
Deuczwild Posted June 19, 2015 Author Report Share Posted June 19, 2015 You know strm trpr I would send it out but shipping would be to much I've been doing my own work on snowmobiles last ten plus years or so. So I think I can handle it I do have a Clymer on hand and I just eyeball carbs been doing it on snowmobiles never had any problems. 1 Quote Link to comment Share on other sites More sharing options...
Deuczwild Posted June 19, 2015 Author Report Share Posted June 19, 2015 This is an awesome read about power valve cheetahs. http://bansheehq.com/forums/index.php?/topic/155869-421-cheetah-pv-vs-421cub/?hl=cheetah yea I've read this one a couple of times now 1 Quote Link to comment Share on other sites More sharing options...
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