ok , i'm thinking of building a cr500 powered cr250 tard . would like to hear from peeps that have used this motor , pros , cons .
yeah... i weigh 150 and couldnt kickstart one for my life... too much compression to be reliable at the consistent high rpm of a roadcourse... maybe if you lowered the compression a little bit and increased the cooling capabilities. that would help you keep your front tire on the ground too
CR500s will shake anything to bits...according to a honda rep I talked to, the wall thickness on the CR500 frames was twice that of the steel framed 250s. despite this advice, a customer of mine installed a CR500 engine in his TRX250 quad chassis, and spent more time welding than riding. After the 4th or 5 frame teardown to weld up some cracked brace, he gave up on the CR500 idea. Service Honda builds the CR500AFs with modern alum CR250 frames, but I honestly dont see how they last.
they also have a green sticker bike that uses the crf250 frame . hmmmmm crf450 powered by 500 , & if you think the cr500 shakes try a vert . just wondering if they are pretty much reliable & how the power delivery/tractabilty on a rr course is w/ the 500 mill . certainly cheaper and easier than 4stroke to rebuild .
I have, my poor nuts! odd tho, when I twisted the throttle WFO, I suddenly became much less concerned about the vibration
i have a 86 cr500 that i love . i have a crf450 also . no comparison at all . the cr500 is the most "fun" & will kill the 4 stroke in a drag race as long as good traction is available . power delivery is terrible on the cr500 , seems like it idles with 20 hp & is VERY eager 2 give the rest of its 60 some hp . the crf450 is the easiest & fastest dirtbike ive ever ridden . power delivery is so electric . my experience is some road racing , alot of drag racing ( dirt & asphaly ), enduro , MX etc , if u r looking 2 have a grin that wont go away , build the cr500 powered bike , if u want 2 have fast consistent lap times & want 2 win a race , build with a 4 stroke or anything BUT a cr500 . regards , Rodger
Central Ohio racer Todd Patton built a CR500 powered TZ250 framed bike as a Clubman racer that ran several years ago. Very fast. I think he had some vibration issues and had to work on cooling it properly but eventually got it sorted out and won a few races with it. I don' t know what ended up happening to it.
We're talking about a two stroke, right? I've never heard of a 2-smoker having that much compression.
you'll need to adjust your port heights and stuff. probably will require rubber mounting the engine. i wonder if they make some kind of counterbalance kit that would cut down vibration?
Wade: its not that the compression is that high, its just that youre trying to compress it all at once, and theres no compression release. Metra: afaik there is no counterbalancer setup for the 500 motor, but you could start with a TRX250R motor which is counterbalanced, and bore/stroke it to a larger size. I built one a few years back that was 370cc and nothing short of a big bore raptor (720cc) would beat it.
2-strokes don't have that much compression ( i'm remembering 9-1 on the 86 cr500 ? ). it seems like the 500's do because of the leverage in the kick start . it is unbelievablely hard 2 kickstart a cr500 , especially the late 80's models . short lever & alot of cc's 2 kick over . in the 90's they made the lever bigger & lowered the power . mere mortals could go faster with the tamer engine . eye opening , arm stretching fantastic fun, but not something 2 hone rider skill . the kx500's had power valves & should b faster & way more controlled power , if i was using a 500 single 2 srtoke to roadrace , i would get a throttle with as far away from a 1/4 turn as they make . regards , Rodger Myers
I had a steel custom framed CR500 some years ago, yep they vibe but if you shave down the flywheel they ain't to bad. Use a 85 or 86 barrel on a 91 and up cases, some you get the most power with the best clutch. As for arm snapping uncontrollable power only true with the stock dirt gearing. If you gear for road racing you get a nice smooth pull almost like a duc. I am now building another one with a TZ250 frame and this one is rubber mounted and the motor hangs much like a RZ350 mount system. you don't kick one over for road race use as you would have frame clearance issues. You send the barrel to Accu-products and they install a decomp valve which makes it bump start just like a 125. Jetting is a real art as the 500 was never really ment to be pinned for a long time as in road race application so one must stay a little wet on the main. With the right porting and pipe 70-72 hp with a insane tourqe curve that will drive you out of a cornner like nothing else.
cr500 racer I built a road racer using tz250 chassis with a 86 cr500 engine i raced it for 10 years and won many races and took lap records with it. it was raced at daytona
