inform me on strokers for the ex

[cals400ex]

i am again in the mood to do more modifications. has any one installed their own stroker? i am debating on doing it given i don't need any special tools. i really haven't checked into it really heavily yet though. how much of a difference will a stroker make vs my current 426? i know the strokers produce torque and what not. i mean drag racing. how many bike lengths approximately would i gain in a drag race from 1st to the middle of 5th gear by stroking it 4mm? i am kind of open to any suggestions on installation or the stroker itself. i am just not sure if i want to mess with it or not. also, i know balancing it is the key. do i need to remove the engine and send the whole thing off for this or can i just send the crank? i don't want to send the whole motor off and if that is what it takes, i think i will pass.

[Silverfox@C&DRacing]

we have talked to a few companies and they don't really recommend the stroker unless you want to replace cases once a year.

[NacsMXer]

Whether or not you need to send your entire motor away to get stroked I think depends on the length of the stroke. I'm not sure if the more common +4mm strokers out there require case machining, but I do know that my +6mm stroker required the lower cases to be machined to clear the crank. I sent my entire motor to GT Thunder and got it back within about a month and a half. I'm really impatient too, but the customer service, professional installation, and reasonable pricing more than made up for the wait. I think i've actually waited to get my shocks back from PEP longer than that. :p
Oh and my previous setup was a 10:1 440 with a 450/451 Webcam, and it is a night and day difference in power compared to what I have now.:devil:

[tdsongster]

FST makes a 502EX stroker kit for about $910.

[cals400ex]

i really don't want to go with a 502. i just want something that i can run a 426 piston in and maybe a 4mm stroke. i think the cases need to be machined only in certain circumstances. i don't remember if it has to do with what crank is used or something like that. but don't quote me on that. also, i know there is something about the rods that i am not too sure of either. certain ones can use the stock pistons while others need the piston pin hole in a different location i believe. i really don't know anything on this subject but i am open to more info and opinions. i really don't know what else i can do to the ex.


dusty, why would you replace the case? you didn't mean rings did you?

[Rico]

Call Laz with your questions Cal..

I agree with Rico call GT Thunder for all of your questions. I had a company do a 463 stroker for me. the company i used is kinda a copy cat of Laz, so it would be a very similar motor coming from him. it is a 426 bore with a 6mm stroke. the bike runs great. I set up everything for woods riding wich made the quad extremely smooth. I believe that nothing was machined. The crank was stroked and ballanced. Custom Rod and piston were used. a low end drop in cam was added with trail porting. Bolted up to a 8 disk clutch set up!

Compared to the 426 I had before. The torque was huge (the 426 was a fully blown national motor and cost more than the stroker) The 426 actually felt faster but I could go faster on the stroker in the woods. drag racing I really don't think there would have been that much difference. But if all you have is just a bore and high comp piston you will notice a huge difference!

[wilkin250r]

I'm extremely curious. Why would you need to replace the cases so often?

I'm not going to waste Laz's time on the phone, since I'm not going to actually buy anything, but I'm still extremely intrigued. Why does the stroker put so much stress on the cases?

Cal, if you DO call Laz, please post the answers.

[Silverfox@C&DRacing]

typically the stroker pistons are 13:1 or higher compression that puts stress on the cases but if you do a stroker that has less compression that isn't as stressfull on the cases. I am just relaying info I got from a couple of companies when we were looking into doing one locally for a customer.

I have never heard of it putting any stress on the cases before. One thing it does put a lot of stress on is the gears! They will need to be check kinda often. If they break it is possible that it could bust a case. maybe that is what they are refering to?

[chad502ex]

Originally posted by Silverfox@C&DRacing
we have talked to a few companies and they don't really recommend the stroker unless you want to replace cases once a year.

I've seen many strokers and have never seen anyone replacing cases, huh?:confused:

[cals400ex]

thanks for the info everyone. this is a learning process for me. for you who don't know what i have now, here it is:

11:1 426, aggressive port job, TC mx grind cam, sparks pipe, modded air box with uni filter, sparks 8 plate clutch, heavy duty timing chain, etc. so, i don't know what else i can do unless i stroke it.


Rico and gncc, i pmed laz on ******** and he didn't reply. i am not too sure why. i don't want to bug him. i just wasn't sure if he didn't want to answer my questions if i was only going to send him the crank for balancing and not installing anything?? :confused: well rico, i did take your advice on the flywheel. i sent it off to laz to get lightened. i am hoping he got that too. i mentioned that to him in the same pm and he didn't get back with me to let me know if he got it or not. i just don't want to bug him.


i only plan on going with the 11:1 as i am at now if i do the stroker. i dont' know, it may not be worth it for what i am looking for. i figured i would be able to raise the gearing a bit and be able to pull more with the stroker. thanks for the help everyone, but i am still open to suggestions. ;)

[Rider#11]

mines stroked..426 piston and 4mm stroke no case machining required...its a bad *** motor..:devil: ..but ya there is a huge torque difference..i recomend the stroke..mines a poweroll

[LS@GtThunder]

Originally posted by cals400ex


Rico and gncc, i pmed laz on ******** and he didn't reply.

, i did take your advice on the flywheel. i sent it off to laz to get lightened. i am hoping he got that too.

;)

I got the flywheel yesterday - but I did not get a PM. If I dont respond to a PM within an hour - send me an email as this is not the first complaint I have had on PMs.

[LS@GtThunder]

Originally posted by wilkin250r
I'm extremely curious. Why would you need to replace the cases so often?

I'm not going to waste Laz's time on the phone, since I'm not going to actually buy anything, but I'm still extremely intrigued. Why does the stroker put so much stress on the cases?

Cal, if you DO call Laz, please post the answers.

Good question -

I have only seen 2 reasons for the cases breaking on a 400ex.

1. Damage from another part such as a chain coming off, a gear breaking, or a rod breaking.

2. Case breaking from the left main bearing forward to the counter balancer bearing - the ones I have seen like this were all on high compression engines, 11/1 compression engines that were run on pump gas, poorly trued stroker cranks, or engines with very high hours. Detonation causes extra stress and sometimes you will see that bearing hammered into the case from detonation to the point that it is no longer held tightly and the vibration of the bearing moving up and down in the case eventually will break the case. This is not caused by strokers but is caused by detonation, fatigue and also from poorly trued cranks. I have seen strokers that were so far out of true that the bearing would rock back and forth as the crank rotated - granted it was only a small amount of rock but after many hours of use it would work itself loose in the case.

[chad502ex]

Originally posted by LS@GtThunder
Good question -

I have only seen 2 reasons for the cases breaking on a 400ex.

1. Damage from another part such as a chain coming off, a gear breaking, or a rod breaking.

2. Case breaking from the left main bearing forward to the counter balancer bearing - the ones I have seen like this were all on high compression engines, 11/1 compression engines that were run on pump gas, poorly trued stroker cranks, or engines with very high hours. Detonation causes extra stress and sometimes you will see that bearing hammered into the case from detonation to the point that it is no longer held tightly and the vibration of the bearing moving up and down in the case eventually will break the case. This is not caused by strokers but is caused by detonation, fatigue and also from poorly trued cranks. I have seen strokers that were so far out of true that the bearing would rock back and forth as the crank rotated - granted it was only a small amount of rock but after many hours of use it would work itself loose in the case.

well put LS.

Just to add to your comments for everyone else,... when stroking a crank, it's extremely important to have the crank harmonically balance to the new piston to reduce any effects LS described above. Early detonation (lean condition due to octane and compression) causes all the undesired force to be transferred to the bottom end main bearings. Think of the what happens to this undesired force when the detonation occurs before TDC.

hope this helps.

chad502ex.com

[the yella yak]

For Laz-I'm interested in getting my crank stroked 6mm on my 400ex. Do the cases or gears or anything have to be machined down to make it fit? I would like to just send you my crank instead of my whole motor.
Also-Do you offer any 88mm pistons for the 6mm stroker? I would like to make it a 463 or so instead of just a 450. Thanks for all your help.

[wilkin250r]

Originally posted by LS@GtThunder
Good question -

I have only seen 2 reasons for the cases breaking on a 400ex.

1. Damage from another part such as a chain coming off, a gear breaking, or a rod breaking.

2. Case breaking from the left main bearing forward to the counter balancer bearing - the ones I have seen like this were all on high compression engines, 11/1 compression engines that were run on pump gas, poorly trued stroker cranks, or engines with very high hours. Detonation causes extra stress and sometimes you will see that bearing hammered into the case from detonation to the point that it is no longer held tightly and the vibration of the bearing moving up and down in the case eventually will break the case. This is not caused by strokers but is caused by detonation, fatigue and also from poorly trued cranks. I have seen strokers that were so far out of true that the bearing would rock back and forth as the crank rotated - granted it was only a small amount of rock but after many hours of use it would work itself loose in the case.



Are the stroker cranks more likely to wear out and be out of true?

I know a bigger piston can do it, the greater mass of the piston will increase the momentum and and inertia of the piston, therefore increasing stress and wear on the crank (a problem that often plagues big-bore 250r motors). Since the stroker cranks have a longer stroke, you are also increasing momentum by increasing piston velocity, but I don't know if it would be more or less significant than piston mass.