gasmask34 Posted January 13, 2009 Report Posted January 13, 2009 You did...I just wanted to dispel this rumor...because numbers tend to stick in others minds more than anything... cool!!! no hard feelings...understand that... Quote
alcoholbanshee Posted January 13, 2009 Report Posted January 13, 2009 cool!!! no hard feelings...understand that... As said it is all trial and error............... What runs good on one engine will not run good on another. I know from my experience my stock stroke 69 bore Cheetah ran much better with big bore pipes. Now my 421 cub ran better with small bore pipes. The cub was ported by Trinity and the Cheetah was ported by Grand River. With all that said I know if Andy ported the cub it would have ran better with big bores........so in conclusion...Listen to your builder!!!!!!!!! Quote
RadarRacing Posted January 13, 2009 Report Posted January 13, 2009 Listen to your builder once again is my vote. My 421 CUB runs better with BB shearers, had more torque and I was told it might not rev quite as far but it's peak hp and torque was at 10K ,it had 90% of that in the 8K to 9K range as well. I'm running inframes too. A good builder that's tested pipes on the dyno will know just listen to him. Radar Quote
rb0804 Posted January 14, 2009 Report Posted January 14, 2009 Listen to your builder. When i was looking for pipes for my bike I heard good things about Shearer's pipes, but i had one question, big bore or small bore. I called and talked to Matt in depth several times and I explained to him my engine combination and what i was wanting to do with the motor and asked if he could recommend a pipe. He said the builders that he sells too all use the small bore pipe for that kind of application except for one. That one builders engine will run with or better than the motors with the small bore pipes. This means its more of a port timing/engine combo choice. To the best of my memory the big bore pipes were made for strokers and have a lower operating range. The small bores are made for more of a "hi rev" application. I would bet on the right motor that big bores would yield a wider, more usable power band which in many cases makes the bike faster without having a high peak HP number. sorry for the long post. Quote
banshee4201 Posted February 26, 2009 Author Report Posted February 26, 2009 I really appreciate all the feedback, i'm just trying to get everyone's opinion. Matt shearer did say small bore. My cylinders are fully drag ported by trinity racing, i have 38pwks on alky, 25cc domes, override trans, 19/38 gearing. I've heard different people say that big bores die off on the top end........ Decisions Decisions Thanks again for the input Quote
J-Madd Posted February 26, 2009 Report Posted February 26, 2009 Anyone got back to back dyno runs with sb vs bb on a 421? Ya'll got me wanting to try BB on my 421. Running sb RDZs now, and love 'em. Quote
badassbanshee479 Posted February 26, 2009 Report Posted February 26, 2009 no back to back comparesons but my 421 cub had small bore rdzs on it, switched to bb shearers, bike seemed to pull a bigger gear easier but would not rev out as far as the sb's would... I sold the 421 to my brother who is trying to buy a set of sb shearers for it right now, so this spring we will be able to back to back track test it with both sets. so far to date with the bb shearers the bike went 4.08 in 300ft. more to come stay tuned Quote
J-Madd Posted February 27, 2009 Report Posted February 27, 2009 That's my fastest time as well!! (not counting a 4.01 at the questionable Planet Sand race last year). Mine seems to pull any gear or tire I try with it. Might be the clutch slipping a hair off the line, I don't know. Quote
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