Author Topic: how good are these psi motors? (Read 9265 times)

mennis1971 · « **Reply #15 on:** February 28, 2014, 10:39:27 PM »

Neil I've heard that same story but from a different source. He was fast when it ran, but he also toasted several motors and that was just in one race weekend. I'm not trying to talk bad about these motors as I have no experience with them.

rsss396 · « **Reply #16 on:** March 01, 2014, 08:17:31 AM »

If I had to guess it would be the design of the head that may of led to detonation issues when the motor was pushed hard and got hot, not sure if you can bolt on a differant style head on this motor or not.

C-Leigh Racing · « **Reply #17 on:** March 01, 2014, 01:25:03 PM »

Quote from: rsss396;27214

If I had to guess it would be the design of the head that may of led to detonation issues when the motor was pushed hard and got hot, not sure if you can bolt on a differant style head on this motor or not.

I cant for the life of me, remember the member got that PSI top end to work, but best as I can remember, I believe he had a guy on Mac Dizzy machine him a new head for it. For some reason the name Kelsy, comes to mind who machined the head, that sled guy I think what he deals with.
Neil

rsss396 · « **Reply #18 on:** March 01, 2014, 02:29:36 PM »

could be Kelsey is RK Tek and he does allot of snowmobile heads, he is a member on the other board also.

86honda250 · « **Reply #19 on:** March 02, 2014, 07:34:45 PM »

The old man and I have a puma and a psi 425. The psi we found worked the best with the sheara puma inframe pipe. We also use 48 mm lectrons carbs. The dial dome we set it to make and it was 13/1 compression so we got our builder shave and reshape the doom to 14.5/1 for race gas and have not touched it sines. Same guy ported my puma as the old mans psi and they were dynoed on the same dyno. The psi made 68 hp and I can't remember the torque. My puma with the CPI pipe made 75hp and I want to say 46 ft pounds but I am not positive about that. Needles to say the last time me and him were racing in Oregon from a rolling start he would cheat and leave before me. By the top of 4th gear I was always 3-4 bike length in front of him. We found with the psi the biggest thing holding it back was the psi pipe. We went from like 61 or 62 hp to 68 with matts pipe. We also picked up 3or4 hp going from a 39 pwk to the 48. Also this dyno is hard for number. In the sled world stock sleds are reeding 15-20 hp less then you reed on the internet.

86honda250 · « **Reply #20 on:** March 02, 2014, 07:40:22 PM »

O ps yes the psi always runs 200 to 220 with the afco rad and my ran about 150 with the afco rad dune riding. My puma now is about 170 with just a oversized rad after my afco started leaking. We also never ran psi's card.

1986trx250r181 · « **Reply #21 on:** April 02, 2014, 04:48:34 PM »

Hey this is a interesting little read. I am in the middle of doing a dune build with one of these engines. The motor I am using has the yz 490 rod with the kx 500 piston. Should put it around the 465cc mark. I will be running race gas. I got the engine running very well before I stripped the bike for the build. I am excited to get it to the dunes to see what it will do. I will keep you guys posted on the build!