yz167

[RICKLAMBERT]

I am considering sending my yz 125 motor to RPM for a 167 stroker kit. Does anyone out there have any experience w/ the motor or Rick Peterson ? Thats a lot of $$ and Im wanting to hear some opinions on this before plunking down 15 hunnert smacks.thanks

 

[WWR]

I am not extremely familiar with the RPM 167 motor, but I do believe they do press a steel sleeve in for this mod. Am I correct? If so, it sure is an expensive way to ruin a perfectly good engine.

Obviously, if you are looking for a 167, you will not be racing this bike because it will not be legal. Assuming that is the case, you are better off going out and purchasing a 250. Just the power you will need, and a huge increase in reliability.

If you are racing, there are much better, perfectly legal ways to make that bike rip. In fact, for that much money, you can have not only a ripping-hot engine from Eric Gorr, but you can also have your suspension completely redone by a professional, to your weight and riding style. And suspension, by far, will allow you to go faster on a track than just engine mods.

By the way, I purchased my YZ 1.5 years ago for $1900. I cant imagine wasting close to that much to ruin a good 125.

 

[KawieKX125]

It is a plated and bored cylinder, not sleeved. I hear they are quick, but I would just go with one of eric's 144 kits or if he can do it, a 154 kit. Cheaper and with the extra dough you could get the all important suspension mods.

 

[EricGorr]

The 167cc kits are constructed this way, its a combination of a larger bore and longer stroke. The cylinder is stripped clean and heli-arc welded to stregthen key areas of the cylinder. Then its bored and the ports are adjusted to bring the timing in line with the crankshaft mods (stroking). Rick doesn't use sleeves in the 167cc kit, he plates a nickel composite right on to the aluminum for the best heat transfer characteristics, besides theres no room for a sleeve in the stretched-out cylinder. Next the exhaust valves and head must also be modified to compliment the bigger bore and longer stroke. Rick prefers to machine the recess of the head deeper to accomodate the longer stroke rather than usespacer plates under the cylinder base that may look obvious or cause spacing problems with the pipe of top engine mount.
After the top end is completed the bottom end gets attention. Rick lenthens the stroke distance of the crankshaft by repositioning the big end pin farther from the center of the crank. There are two popular ways to accomplish this depending on the design of the crank.
If you're serious about spending the money on a big bore, remember that theres many other parts that may need to be replaced while the engine is apart for mods. Things like bearings, seals, gaskets, clutch and tranny parts, etc. It all depends on the condition of your engine. You'll also need to budget money for shipping and insuring the engine, that costs about $40 in each direction (2x40=$80). A typical performance rebuild like this could be as much as $1800-2000.
If anyone from RPM is reading this, please post any info that I may have overlooked.
Good luck with your decision.

 

[firecracker22]

I have ridden a friend's 2000 RM 167 and it was SWEET. I didn't see you reply to the racing question, but there is room for it on open and age group classes, or of course off road, cc classes are set up differently.

Compared to my KTM 200, the 167 was smoother. Not as much torque--although much much more than a stock 125 of course--but sooo smooth, you could just roll on the throttle. I liked it so much that when/if I get rid of the KTM, a 167 will be my next two-stroke. I wouldn't get the RM though, I'd go with the YZ or CR.

Anyway, I liked what I saw the little I got to ride that RM 167. It made good useable power and didn't feel out of balance, pipey, or flat. I didn't like the rest of the bike (clutch handling etc) but if you plan on keeping the YZ, I don't think you'd regret it. Of course, keep in mind you will not get your money back when you sell.

 

[RICKLAMBERT]

im 35 yrs old & ride cross country & trails. We have a HUGE SX style track outside of town. I own a 426 & a 125. ive heard a little about the 167 but i was happy to hear your testimony. I think the 167 would be the perfect tight woods bike, but im a little concerned with overheating in 100 degree summers we have here. What about that?

 

[RICKLAMBERT]

Thanx Eric. I appreciate the info. Im saving my $$ !!

 

[yz 200 guy]

WWR is way off base on the racing thing. If you are doing MX, there are age classes (16-24, +25, +30, +40, etc.) where cc's are not an issue. You can race any size bike if that is what you go fastest on.
Off road racing has the A and AA classes where again, any size bike is OK. B classes out here are 0-200cc and then 201cc and up. Iowa for 2002 is going to let KDX220's and the 225cc 4 strokes race in the smaller B class.

2 years ago I wanted to do a YZ167, so I called up Rick Peterson @ RPM and talked to him. He was very helpful and sent out a packet of dyno charts and customer testimonials. After seeing these, I think it is irresponsible for someone who admits to knowing little about his work (steel sleeve?) to say that it ruins a good engine. The '98 YZ167 dyno test I saw showed 38+hp with a broad torque curve - that is one of the keys to an easy to ride motor.

I think a 167 would be cool, but it is very $$, and you won't get your money out of it come sale time. Smile time, it could be worth every penny. Rick will also talk to you and show you dyno tests of his 134 and 144 YZ's which are not strokers. Rick will tell you that YZ's seem to respond the best to the 167 treatment of all the Japanese brands.

Then I'd call up Eric and get his advice on his big bore work. If you build something, please let us all know what you think!

 

[jake949]

do a search on big bores and you will find a dyno that canadian dave put up a while back i saw it yesterday, it compares a kdx-yz167-stock yz125-and some EG rm150.