please help, 379 hot rods stroker

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Well-Known Member
Aug 6, 2012
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ok im new to messing with the internal engine parts. i have what i believe is a 91 warrior. i want to put in the hot rods +4mm crank(379cc). i am unsure on what piston to get. hot rods says you have to use their piston(P3001), i know you can use other pistons as i have seen it on this site. i am doing this as a senior project and could use any info you can offer. so my question is what piston would go best with the stroker for the price, i have found the hot rods piston for about $105. would this piston be sufficient for my build?
if you use the hot rods piston its about 10.5:1 compression, .040 over, relitively moderate job.

if you use ANY other piston the deck will be off by about .060-.090" off so it will need a jug spacer plate made, cometic gaskets can make one but you will need to know exactly how thick it will need to be.

tools needed to do just the regular 379 stroker is
a flywheel puller.
8mm socket
22mm socket
24mm socket
flat head screwdriver
hammer or rubber mallet
razer blade scaper
a cleaner agent like brake clean
oil for re assembly
bottom end gaskets
topend gasskets
a capable engine shop to bore the jug and change valve seals
a lot of time, this will take you a full day to pull apart, and a full day to put together.

the hadest part is when you split the cases, not to let the trans cam apart its a pain to get the shift forks to go back together.

if you do the regular piston on the HR crank you will need a mic. and modeling clar and a lot of patentce and add another day to the build time.

the only gain with not useing the hot rods piston is higher compression and if you punch it to .080 over its a 388 but you will have engine temp issues and will need oil coolers and shrouds ect.
thanks for your reply. i already have the motor tore down.

is a 10.5:1 compression good or should i go with a higher compression piston and make a jug spacer plate?

if you do the regular piston on the HR crank you will need a mic. and modeling clar and a lot of patentce and add another day to the build time.

not to sure what you mean by a mic. and modeling clar.
clay* you will need to set deck height, it all depends on what your wanting to do with it.

if you want a low rpm thumper trail machine just a 10.5:1 is fine.

if you want a really snappy hast bike go with a higher comp 11.5:1 or so, if you go over 12:1 it will require race fuel. anything over 13:1 will take new head bolts. and anything over 13.5:1 has never been tried on these motors.

it all depends on your plans with it are, and what else you are gonna do to the machine, are you gonna change carbs? exhaust? cam? oversized valves? porting? suspension? all play a role into what would suit you best.

oh and by the way, Welcome to the Forum!
He means micrometer and molding clay. The 10.5:1 is plenty for most people. I will have my stroker together hopefully buy next weekend. Just waiting on my top end to get back from the machinist's. I am planning to run it without the base gasket, like Weston does on his engines. Should get the comp up to 11.25:1.

Another option is to get a big bear or kodiac 400 cylinder, and have it milled down to the proper height, so you can run a standard high comp piston in it. It's either run what you have, make a spacer, or mill a cylinder to get it to work.
Thank you glad to have found it, lots of good info on here.

I do a lot of trail riding but I would like it to have some good speed to. At least to keep up with my buddies stock z400.

I was thinking about getting some aftermarket cams. Pretty new to this stuff. Right now I'm mostly concerned with the crank and piston. Probably do more as money comes in. Don't get far on a part time job.

My motor locked up on me sometime around September. Believe its the connecting rod bearing? Found some metal in the bottom of the motor and a lot of metal shavings in my oil filter. Also my crank has what looks like a burnt spot. I have some pics in an album.

One more question, this is not the original frame, not sure what frame it is and unaware of the year of the motor. Is there anyway to find out the year by the engine serial? I narrowed of down between I think was 89-93 due to my throttle cable splitting in to two into the carb
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If the characters 1UY appear anywhere on the engine, it is a 1st gen 87-88, if memory serves. I think the 87 vin had H for the year designation (10th character) and 88 had a J. Also, if your head lights are mounted just above the bumper, it's 87-88. If they are square and on the bars its 89-92?. And, round lights is anything after that. If it has a pullstarter, it's a 87-88. If it has a bushing instead of a bearing for the lower steering stem mount, it is an 87. If it has replacable balljoints, it is an 87. If it take 4 bolts to mount the axle carrier to the swinger, it's 87-88. I can go on, lol.
It has 1uy01. But I have no pull start. And I can't check Vin, not original from don't even know for sure its a warrior frame.


you'll be plenty happy with the hotrods stroker kit at the 10.5:1 but your going to want to put in a cam and do a little port work... also looks like you might have a bent valve but could just be the pic ...
Bones is another guy running the hotrods set up. So is Jasonp, and 357warrior. I can't get the pics to come up. Get some type of cam and port work done to it, like Bones said. You're going to get the most out of it, and make a better all around power band. I'm putting the biggest cam made for them in mine, so we'll see how it goes. MAY have to run a smaller cam, but until I get it together and hit the trails, I won't know for certain. If you are unfamiliar with reading and understanding cam profiles let us know.
Actually powroll has a custom "stroker" cam custom ground for them that is huge on duration and more then the megacycle .450.
With the hotrods crank you can pretty much get away with running any piston you want will just have to get adjustable cam gear when you adjust for deck height with custom gaskets.
Best would be just go with the vertex piston hotrods offer with a stage 1 hotcam. That would be a good woods pump gas engine.
I just looked and it seems the newer vertex piston for the stroker crank is 9.2:1 compression. I thought it was around 10.2:1.... might want to think about going with a different piston with more compression if your going through the trouble. What you guys think?
Last time I was on hotrods site they said that the new pistons are forged 10.5:1. Give them a call to verify. I bought one off jasonp because he went with a different piston. I forgot about the Powroll cams. I thought that Web makes their cams?