RoostRocket Posted February 22, 2007 Report Posted February 22, 2007 I just got my shee back from the shop with new modquad head w 19cc domes and vf3s and it screams!!!! but the compression was 150psi and if im correct it should be 200 210psi were im at so im thimking about going all out on a new 421 cub... but my question is will it be hard to ride on anything but sand by the way i converted from 4 pokes recently after 5 min. on a banshee :biggrin: please help i may just have the top end rebuilt thanks for the help. Quote
locogato11283 Posted February 22, 2007 Report Posted February 22, 2007 whats your elevation? most people dont run compression around 200. what kinda riding do you do and what are you trying to get out of a motor? Quote
bigscary Posted February 22, 2007 Report Posted February 22, 2007 a 421 is too much for trail riding.... unless you do a LOT of drag racing..... I have a 350 cub and it is almost too much.... Quote
2bzy2p Posted February 22, 2007 Report Posted February 22, 2007 agreed! although i am amazed to see how many people at the dunes have the 421 cub in an mx set up and they say they love it!???if it was me id set it up to drag race with the cub it is tripple ported which is mainly for drag racing !! WOT Quote
Animalman294 Posted February 22, 2007 Report Posted February 22, 2007 I doubt even at sea level that you will get 200 or 210 psi with just 19cc domes. Your 150 does sound right, but thats my .02. You need to do more research before you go all out cubby............ :thumbsup: Quote
RoostRocket Posted February 23, 2007 Author Report Posted February 23, 2007 thanks for the help guys i slept on the thought last night and have come to my senses a 421 cub is not for me right now i am at sea level but the guys were telling me that 150 was way to low but i trust hq guys more than just some random "shop rats" as my husband calls them. thanks again for all the help Quote
06BaNsHeE Posted February 23, 2007 Report Posted February 23, 2007 thanks for the help guys i slept on the thought last night and have come to my senses a 421 cub is not for me right now i am at sea level but the guys were telling me that 150 was way to low but i trust hq guys more than just some random "shop rats" as my husband calls them. thanks again for all the help Well at sea-level with 19cc domes and a wicked atv head I was at 176 and my old builder told me that was about right but with a fresh bore I would be at 185 .But 150?Dont you go up to like 155-160 with 21cc domes? Quote
Handyman Posted February 23, 2007 Report Posted February 23, 2007 My cheetah P.V. is running 175psi with 20cc domes at 200ft above sea level. if I put 17cc domes in it will go up to about 210-215psi. Quote
warbags Posted February 23, 2007 Report Posted February 23, 2007 Make sure you use a good compression tester and not some $20 tester,I made that mistake[cheap tester 90psi,MAC tools tester 120psi]still need to rebuild the topend but thats a big differance. Quote
RoostRocket Posted February 23, 2007 Author Report Posted February 23, 2007 I just did a compression test on my wifes banshee (this is not bansheebabe04) and i got 145 in both cylinders with 19cc domes. im at sea level or close to so im sure it should be higher but is a top end rebuild nessesary now? thanks for the replies. by the way i contacted the guy thats the work on my yfz and he said i dont need to run race gas cuz of the low comp. Quote
bigboybanshee Posted February 23, 2007 Report Posted February 23, 2007 I'm between seal level and 400ft, running 20cc domes with a lightly ported engine and am getting 159 psi in both my cylinders. I would see if you can get another gauge just to make sure you get the same numbers. Just curious, but are you holding the throttle wide open while you're kicking for the compression test? If so, and the numbers are the same with another compression tester, then I would be looking into rebuilding the top end Quote
majicmike Posted February 23, 2007 Report Posted February 23, 2007 My cheetah P.V. is running 175psi with 20cc domes at 200ft above sea level. if I put 17cc domes in it will go up to about 210-215psi. You cheetah is a larger bore you need more cc's in the dome compared to a 64mm bore :thumbsup: Quote
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