G
Guest
Guest
Be keen to see how that goes!
Any idea of the cc's after boring it out?
Any idea of the cc's after boring it out?
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Has anyone done 69mm Wiseco GS750 10.25:1 844cc pistons in a GS400/425?
- Thread starter Chuck78
- Start date
B
bogmonster
Guest
Runs strong
Runs strong
got out for a few short shakedown rides, so far impressed with the power. I never rode the bike before the motor work so i cannot comapre to stock performance. I will say a buddy was on his xs 650 ,and he was having trouble keeping up even though i was being easy on it to break in the rings.
Plan on getting it on a dyno this winter for the final tune. More pics to come
Runs strong
got out for a few short shakedown rides, so far impressed with the power. I never rode the bike before the motor work so i cannot comapre to stock performance. I will say a buddy was on his xs 650 ,and he was having trouble keeping up even though i was being easy on it to break in the rings.
Plan on getting it on a dyno this winter for the final tune. More pics to come
No but I still plan to in the next year or so - but I accidentally happened upon enough spare parts to build my spare bike as a '77 or '78 gs750 instead of a gs twin. Definitely wanting to build up a stripped down hot rodded gs twin 449cc 10.25:1 compression in the future. It should be no different than a standard rebuild other than tuning & jetting, & I think the 10.25:1 pistons with the 400 heads will yield a little more than 10.25:1 that is advertised with using the 750 head. The 750 advertised 8.8:1 compression, the 400's advertised 9.0:1 stock.
back from the archives, I just picked up a spare seized GS 425 engine, as the engine in the 425 has great compression and I don't want to tear it down!
I will probably do a 4 millimeter overbore, same as the Wiseco kit in the GS750 844cc's, assuming that the cylinder wall thickness on the 425 wasstill the same as the cylinder wall thickness in the 400 &750.
using the same pistons that will take an 850 cylinder in a 750 up to 894cc @ 11:1, the GS425 would knock down 475cc & 11.4:1. not sure if this is too high for 91 octane, but I would be running upgraded cams with bigger duration than stock, so it may be completely streetable. I'll have to ask around to some of the more experienced engine builders here. at that compression ratio, I would probably want to fit an oil cooler.
if I end up going 798 cc 11:1 with some new old stock pistons I found, and not custom JE Pistons 894's, then I may look into having rapid ray resleeve this spare 425 cylinder block to go 502cc or 516cc with gs1000, 1100, or 450 sleeves, and the ultimate - Carillo's CP Pistons custom for this bike. I was going to try to get slightly better pricing than $680-ish for 4 custom JE Pistons by ordering 6, same for the Rickman GS750 & the GS425, or 8, or 10... if I find anyone else looking to do the same on a 750, 850, or GS425. that would drop the price per piston down a bit.
Ray - I plan on sending you at least one or two heads this winter for some work! Need to get your phone number again and give you a call sometime early winter to discuss.
I will probably do a 4 millimeter overbore, same as the Wiseco kit in the GS750 844cc's, assuming that the cylinder wall thickness on the 425 wasstill the same as the cylinder wall thickness in the 400 &750.
using the same pistons that will take an 850 cylinder in a 750 up to 894cc @ 11:1, the GS425 would knock down 475cc & 11.4:1. not sure if this is too high for 91 octane, but I would be running upgraded cams with bigger duration than stock, so it may be completely streetable. I'll have to ask around to some of the more experienced engine builders here. at that compression ratio, I would probably want to fit an oil cooler.
if I end up going 798 cc 11:1 with some new old stock pistons I found, and not custom JE Pistons 894's, then I may look into having rapid ray resleeve this spare 425 cylinder block to go 502cc or 516cc with gs1000, 1100, or 450 sleeves, and the ultimate - Carillo's CP Pistons custom for this bike. I was going to try to get slightly better pricing than $680-ish for 4 custom JE Pistons by ordering 6, same for the Rickman GS750 & the GS425, or 8, or 10... if I find anyone else looking to do the same on a 750, 850, or GS425. that would drop the price per piston down a bit.
Ray - I plan on sending you at least one or two heads this winter for some work! Need to get your phone number again and give you a call sometime early winter to discuss.
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