Hotrods 4mm stroker cranks. Anyone fitted one?

[BC250R]

I need to buy a new crank assy for my 86 ATC250R.

I'm definitely going the 87-89 TRX long rod option with 86 piston and spacer plate. Hotrods have these cranks available as standard and 4mm strokers.

*Has anyone used the stroker?
*Do you have to bore out the cases to clear the extra swing of the crank?
*What happens at the head when the piston is pushed an extra 2mm up?
*Does the head or piston need to be machined for clearance?
*And MOST IMPORTANT, if you have to do any of this, are the results worth it?

Thanks in advance for any helpfull advice,

Cheers, Brett.

[BC250R]

Um, I guess this means no one has huh?

[Billy Golightly]

From what I understand the crank fits in the cases fine without any mods. You'll need to re-cut your head dome deeper then stock or run a spacer plate to compensate for the extra stroke.

[rich250rracer]

I need to buy a new crank assy for my 86 ATC250R.

I'm definitely going the 87-89 TRX long rod option with 86 piston and spacer plate. Hotrods have these cranks available as standard and 4mm strokers.

*Has anyone used the stroker?
*Do you have to bore out the cases to clear the extra swing of the crank?
*What happens at the head when the piston is pushed an extra 2mm up?
*Does the head or piston need to be machined for clearance?
*And MOST IMPORTANT, if you have to do any of this, are the results worth it?

Thanks in advance for any helpfull advice,

Cheers, Brett.

I built one for a TRX cross-country/harescrambles quad. The cases will need some minor work, but it can be done at home. The cases need to be relieved at the front and back, just the small corner that protrudes into the crank area. I can't remember if an '86 piston has to be modified, but an 87-89 does. The skirt must be cut on the bottom or it will bottom out on the crank. The cylinder head WILL need to be rechambered. I found the easiest way to check your clearances is to put the crank in the right side case (this side will usually slide in), put the piston on the rod with no rings or circlips, and slide the cylinder over and all the way down. With no left case, you can spin the crank by hand (SLOWLY) and look for clearance issues.

[BC250R]

Thanks guys for the info.

Hotrods listed a stroker piston, maybe this address the skirt length.

So rich250rracer, how did the motor go? Was it worth the extra effort? or would you just stick with standard stroke and chase performance gains elsewhere? The stroker is only an option as i need to buy a crank assy now and they are available. What would you suggest?

Thanks again, Brett.

[hrc85250r]

first of all, what are using the motor for? it might not be worth it, and i have built a motor also, and the cases didnt need to be touched at all, and you use an 85-86 piston. the dome will need to be cut 2mm deeper, even easier if you have a coolhead, just call someone up and tell them you are running the 4mm stroker with an 86 piston and they will know what you need, 50$ later you have the dome.

[rich250rracer]

Thanks guys for the info.

Hotrods listed a stroker piston, maybe this address the skirt length.

So rich250rracer, how did the motor go? Was it worth the extra effort? or would you just stick with standard stroke and chase performance gains elsewhere? The stroker is only an option as i need to buy a crank assy now and they are available. What would you suggest?

Thanks again, Brett.

Alot will depend on the pipe you run, there's many more choices out there for the TRX, I'm not sure what's available for the ATC. The motor has unbelievable grunt right off the bottom, so much that it can launch easily in second gear and maybe third, depending on conditions. First gear is almost useless, unless you re-gear. Works excellent for a woods racer. It has a Paul Turner Type 6 "woods" pipe on it, which I absolutely don't care for, way to much short shifting. The guy I built it for loves it, but if it were mine, I would try at least a mid-range pipe, and let it stretch it's legs a little.

[rich250rracer]

first of all, what are using the motor for? it might not be worth it, and i have built a motor also, and the cases didnt need to be touched at all, and you use an 85-86 piston. the dome will need to be cut 2mm deeper, even easier if you have a coolhead, just call someone up and tell them you are running the 4mm stroker with an 86 piston and they will know what you need, 50$ later you have the dome.

I can't see how the rod didn't hit at the front and rear of the case. If I didn't relieve the cases, it would bind up.

[BC250R]

Ok i've found out a bit more info aswell.
Spoke to Hotrods tech advisor and he told me that they do not list a piston for this crank so i will have to do some work to the skirt.
He claims that you shouldn't have to touch the cases but there have been some exceptions.

I do have a Coolhead and it just so happens it is heading for the lathe anyway to have it o-ringed and some compression relief so it may aswell get 2mm clearance while it is there.

I use my ATC250R only on sand, always having its neck rung (is there any other way) for everything from tight twisty tracks through small dunes, drag racing, W O T long straight flat tracking you name it Stockton sand dunes in Newcastle Australia has it. At "Stocko" there is always heaps of super competive social riding (read unofficial racing), trikes verse quads, mines faster than yours, my dad could beat up your dad etc. etc

Oh and there is the other Aussies with the shiney trikes that ride out, park them and take photos and talk the talk. (They get in magazines)

My bike has
* CT Racing mid-range pipe with CT muffler
* 38mm PJ hopefully to be replaced with a 39PWK when one pops up
* K&N air filter with outerwear and no airbox
* Reed spacer and carbon tech reeds
* PVL full ignition system with super small and light flywheel (to be fitted with this rebuild)
* a TC National heavily ported cyclinder with a 66.5mm Honda piston
* Prodesign Coolhead with 20cc dome, to much compression for pump gas.

Hope this info helps you guys point me in the right direction.
Thanks yet again, BC