carb boring .... 39pwk to ....
carb boring .... 39pwk to ....
did anyone bore there own carb ? i have never bored one so is it just the cylinder side ? is the airbox side taper also done ? any info would be cool
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100hp honda
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i wish i had machine shop in my garage but i dont. the ones i seen were bored on both sides. you might be able to bore the aircleaner side then flip it around and bore the engine side so you dont have to pull the center apart. or you could pull the center out but i think some of those parts are not available for individual purchase so dont mess anything up. really the best way is bore it through continuasly so its straight line
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100hp honda
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cheers100hp honda wrote:you might call a carb expert to get a second opinion, before you get started. when i had a pwk bored out, it was straight bored and worked great. the only good advice i could give you is becareful do dont bore it too much, particularly around the slide area.
when i pull the slide out i will measure the flat face of it for my limit , TBH i will just go .5mm for a start .Haha... been grave diggin...LOL
PWK---center bored mine to 41mm, then offset bored it upwards to 44mm.
Shaved 5mm off the top of the slide so it cleared the new 41x44 bore.
The motor had Eric gores port work, with additional aggressive intake and the additionaly the bridge removed , +1mm base gasket, and recut head, .038" PTH clearance, and 14:1 compression.... It was retarded.... I loved it!
Should never have sold that bike.
My own built CR500AF, built back in 2003.
I prefered the PC pipe to the fatty...BTW
PWK---center bored mine to 41mm, then offset bored it upwards to 44mm.
Shaved 5mm off the top of the slide so it cleared the new 41x44 bore.
The motor had Eric gores port work, with additional aggressive intake and the additionaly the bridge removed , +1mm base gasket, and recut head, .038" PTH clearance, and 14:1 compression.... It was retarded.... I loved it!
Should never have sold that bike.
My own built CR500AF, built back in 2003.
I prefered the PC pipe to the fatty...BTW
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Roostius_Maximus
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what made you like the pc?
nice work on the carb, dad ran the same style bore on his sleds back in the day and on his '87 500s PJ, "the pear" he called it
nice work on the carb, dad ran the same style bore on his sleds back in the day and on his '87 500s PJ, "the pear" he called it
http://www.youtube.com/user/500bigbore
My CR500 Tech Reference... http://sdrv.ms/1a0CIiz
MRE Components... http://sdrv.ms/1bs2zhd
My CR500 Tech Reference... http://sdrv.ms/1a0CIiz
MRE Components... http://sdrv.ms/1bs2zhd
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dannygraves
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DeWayne talks about those oval bores. says when theres no more room to go out, just go up 
I bored my mikuni to 42mm. mikunis are easy though because you just revome the needle jet a strait bore it all the way through.
I bored my mikuni to 42mm. mikunis are easy though because you just revome the needle jet a strait bore it all the way through.
'09 kx450f 4-Poke
Gen-4 trail bike --SOLD--
Gen-3 badass trail/mx bike --SOLD--
Gen-1 built dunes bike --SOLD--
'05 klx110 --SOLD--
'95 pw80
Gen-4 trail bike --SOLD--
Gen-3 badass trail/mx bike --SOLD--
Gen-1 built dunes bike --SOLD--
'05 klx110 --SOLD--
'95 pw80
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britincali
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dannygraves
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Thanks roostious...
I liked the top end over rev better with the PC pipe. With the added compression, carb and porting it was agood balance. It felt a bit smoother, but more on top, and a bit less in the middle maybe.
As for the carb the top bore was still 41mm, just offset 4mm,
so in essence it was an oval bore 41x44 tall
It was a real pain to jet, I ran c-12 in it.
I still have about 8 needles, and some big main jets I kept.
I ended up with a 192 main, and a crazy needle too... it was moving some air! LOL
I had a hrd time getting the right taper and diameter combo.
I squeeked it once, then ended up using a EGT, but still difficult to get right
About then the PSI carb had just came out, and grew to appreciate such a device. Never did use one but I could only dream...LOL
The jug was bored over .080, and the recut head was 37cc I can't remember the width of the squishband.
I know we chopped a pile of the face, then reangled, and then finnished the squish band and blend into the bowl.
So, ya the uncorrected compression, was 14:1, 502 divided by 37 according to my math.
It made 210 psi on a warm wet compression test. I was bored beyond the decompression grooves, and did not want them there.
I suppose I could dig up notes, cause I kept a binder full of them. This was the 4th bike with about 11 engines ported under my belt.
I was just following graham bell, eric gore, and a few other pretty intelligent people though my trials and trivilations
There is no way you could kick it through the compression stroke.
I had a few different heads, with different squish bands cc, and pipes to try. Typical PITA , lean it over and check the float, rock it in gear and charge the cylinder, nudge it past TDC, and kick it like a mule.
I tried raising and lowering the decks, and moving the timing around too.
Other than exhaust tunnel ports, it was pretty radical for me anyway.
Anyone wo rode it came back and was grins ear to ear. It had big power, felt like a street bike, yet the configuration i settled on smoothed the hit and had wicked over rev. I think it just made so much more before and after the hit, that it just plain felt strong instead of stupid at 5K, then on its face just as fast.
It ate my stock 98CR500, and in heads up killed my stock87 CR500 as well.
I went through some financial difficulties in 2005 and sold all but the AF, then in 2006 eventually sold the AF too.
C-12 got expensive, PITA , but once you have ran an engine that actually NEEDED 108MON, the rest honestly feel boring by comparison.
Oh, I had it geared 15-47 so the tire would have 1/2 a chance hooking up.
It was riden on Sandy fire roads that were whooped out, and typical speeds were WFO for most bikes, then i would snick it into 5th gear and laugh inside my helmet.
I have seen many kickstarters on many 500's break off from guys trying to "heman" it through the compression stroke....haha
I won't ever even think I know more than the next guy, cause thats when I get schooled...LOL
I had the old handle dubious, on here quite a while ago now....~ 2003
Its good to be back though. I am really excited about my next build.
I am considering a CPI jug, pipe, and PSI carb...
I will probably build it in a steel frame then worry about the conversion next winter
what ya all think?
still undecided in my direction, but have been looking at local bikes and got some options lined out.
Kinda thought about the KX500AF too ....eeeks...LOL
I have never owned one, but the port layout looks like is alot easier on rings than a wild CR500 port job.
Ice Racing, Duning and just demoralising are my objectives.
I know it will be way too much power for a track or trails,
Should be about perfect...LOL
I liked the top end over rev better with the PC pipe. With the added compression, carb and porting it was agood balance. It felt a bit smoother, but more on top, and a bit less in the middle maybe.
As for the carb the top bore was still 41mm, just offset 4mm,
so in essence it was an oval bore 41x44 tall
It was a real pain to jet, I ran c-12 in it.
I still have about 8 needles, and some big main jets I kept.
I ended up with a 192 main, and a crazy needle too... it was moving some air! LOL
I had a hrd time getting the right taper and diameter combo.
I squeeked it once, then ended up using a EGT, but still difficult to get right
About then the PSI carb had just came out, and grew to appreciate such a device. Never did use one but I could only dream...LOL
The jug was bored over .080, and the recut head was 37cc I can't remember the width of the squishband.
I know we chopped a pile of the face, then reangled, and then finnished the squish band and blend into the bowl.
So, ya the uncorrected compression, was 14:1, 502 divided by 37 according to my math.
It made 210 psi on a warm wet compression test. I was bored beyond the decompression grooves, and did not want them there.
I suppose I could dig up notes, cause I kept a binder full of them. This was the 4th bike with about 11 engines ported under my belt.
I was just following graham bell, eric gore, and a few other pretty intelligent people though my trials and trivilations
There is no way you could kick it through the compression stroke.
I had a few different heads, with different squish bands cc, and pipes to try. Typical PITA , lean it over and check the float, rock it in gear and charge the cylinder, nudge it past TDC, and kick it like a mule.
I tried raising and lowering the decks, and moving the timing around too.
Other than exhaust tunnel ports, it was pretty radical for me anyway.
Anyone wo rode it came back and was grins ear to ear. It had big power, felt like a street bike, yet the configuration i settled on smoothed the hit and had wicked over rev. I think it just made so much more before and after the hit, that it just plain felt strong instead of stupid at 5K, then on its face just as fast.
It ate my stock 98CR500, and in heads up killed my stock87 CR500 as well.
I went through some financial difficulties in 2005 and sold all but the AF, then in 2006 eventually sold the AF too.
C-12 got expensive, PITA , but once you have ran an engine that actually NEEDED 108MON, the rest honestly feel boring by comparison.
Oh, I had it geared 15-47 so the tire would have 1/2 a chance hooking up.
It was riden on Sandy fire roads that were whooped out, and typical speeds were WFO for most bikes, then i would snick it into 5th gear and laugh inside my helmet.
I have seen many kickstarters on many 500's break off from guys trying to "heman" it through the compression stroke....haha
I won't ever even think I know more than the next guy, cause thats when I get schooled...LOL
I had the old handle dubious, on here quite a while ago now....~ 2003
Its good to be back though. I am really excited about my next build.
I am considering a CPI jug, pipe, and PSI carb...
I will probably build it in a steel frame then worry about the conversion next winter
what ya all think?
still undecided in my direction, but have been looking at local bikes and got some options lined out.
Kinda thought about the KX500AF too ....eeeks...LOL
I have never owned one, but the port layout looks like is alot easier on rings than a wild CR500 port job.
Ice Racing, Duning and just demoralising are my objectives.
I know it will be way too much power for a track or trails,
Should be about perfect...LOL
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NightBiker07
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Roostius_Maximus
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keeping the first portion of the carb small makes it react like the small bore, keeps some torque in it, and the big side obviously makes it feel like the big carb. We're dooing the same think on the new KTMs and some dude in michigan figured he had a trick setup til he looked at the cuz's and seen we'd already been there 
http://www.youtube.com/user/500bigbore
My CR500 Tech Reference... http://sdrv.ms/1a0CIiz
MRE Components... http://sdrv.ms/1bs2zhd
My CR500 Tech Reference... http://sdrv.ms/1a0CIiz
MRE Components... http://sdrv.ms/1bs2zhd