Kurlon has a dirt project

[Paul_E_D]

I don't know the WR setup, but it is a common wear area and another thing I had to rebuild on my KDX project. Disassemble, clean carbon off, replace worn rotating parts, reassemble with some good grease. It's usually a fairly simple assembly.

[FTMS]

what do you mean sore spot, like needs to be cleaned alot or broken?

With exhaust valves it really depends on your oil that you run. I see it a lot with sleds. I haven't had any problems with mine on my bike and I would bet Seth hasn't hand any problems either by his post. Run good oil and you won't have to clean them much or just run at wide open throttle any they will clean themselves.

[Kurlon]

What's the suggested premix brand? I've just picked up a bottle of BelRay S2, along with the NoToil system to R&R that filter for this weekend.

Full Throttle you say... so... only one spot at MX207 I dare do that at right now... guess I better find a sand pit. : )

[seth399]

Ya I've never had a powervalve issue but have only disassembled to clean/lube. I have heard of broken ones though.
I use Amsoil dominator premix at 40:1

["Dangerous" Dan K]

Ya I've never had a powervalve issue but have only disassembled to clean/lube. I have heard of broken ones though.
I use Amsoil dominator premix at 40:1

I had a powervalve issue, it was so bad I didn't even realize it was supposed to be a moving part (it was also my first time inside a 2 smoke engine). I had to take the engine down twice, the second after someone on here (forget who, but there's a thread on it somewhere) told me about it.

[FTMS]

I am running Golden Spectro at 44:1.

[Kurlon]

Hey... wait, can't I expoxy that sucker closed and guarantee low end throttle response and a power curve you can set a pool table on without shimming? : )

[breakdirt916]

I'd trust others on this, but I just thought power valves assemblies just need kept cleaned.

I guess I'm the anomaly otherwise; I just run a standard 32:1 with suzuki 2-stroke oil

[FTMS]

You would be better off taking an exhaust valve out of the GS and "Kurlonizing" it for maxium performance.

[Kurlon]

I think I found at least one issue affecting how the bike ran. Popped the exhaust off, then opened up the powervalve area. The pic shows what I found. There is a machine screw to the left of the valve pivot point just kinda... hanging out. The valve assembly has an arm with a half circle at the end, like a mini shift fork that is locked in place by the screw. The cases have a hole the screw is set into, but I can't see any signs that there were ever threads there. I also can't find any signs of a screw or pin in that spot on the parts fiche. With that screw in place the valve is locked in the closed position. With it removed the arm from the governor can open and close the valve freely.

Am I correct in thinking that's an assembly pin that isn't supposed to be left in? Is there any adjustment to this assembly I need to bother with?

Edit: I've done some digging, that pin setup is for assembly only. pulling it and will be retesting the motor Sunday hopefully. : ) (After some more de-gunking...)

While I've got the exhaust off, any suggestions on how to clean it out?

[Paul_E_D]

Wow, that's gonna make a BIG difference. I wonder why it's there though...

Clean the pipe by filling it with easy off and a bunch of old bolts. Let it soak a while, then shake and bake (don't literally bake).

[typeone]

Wow, that's gonna make a BIG difference. I wonder why it's there though...

cant wait to read your ride report after removing it. that is just plain odd

[breakdirt916]

I'm a little confused.

So that bolt was put in by Yamaha when they manufactured the engine, and it was never removed?

Why would the bolt be put in there in the first place?

[Fast_Eddie]

I can only tell you that none of the YZ's that I've worked on have that flat head screw. I can only guess that it's either an alignment screw told it in position during assembly or it's somebody's hillbilly engineering experiment to prevent it from having the same top end power that a YZ has. I wonder if that Hillbilly engineer worked for Yamaha?

[Kurlon]

The screw isn't factory. The bike was supposed to ship with a pin that you'd use when working on the powervalve to hold it in place while you tighten or loosen the bolt that goes into the powervalve. Once you're done with that bolt you take the pin out.

[breakdirt916]

got it, thanks

then wow...hold on tight!

[Kurlon]

Hrmm... no signs of an exhaust gasket or o-ring and the air filter just started falling apart as I tried to wash it so no test rips this weekend. D-oh! I'm much more confident that the motor is going to be ok though after figuring that pin out so I'm going to put the initial parts order in, bushings/bearings and bits for the exhaust plus an air filter. I can't re-tap the one bad gastank captive nut, and I need to drill out and tap to the next larger size (8mm) one exhaust hanger bolt. Plus I've got to jump on a couple ebay auctions, swignarm pivot bolt and subframe brace... and this thing might be usable soon. Ugly, but usable. : )

NoToil Fast3 filters, do those come pre-oiled and ready to roll in the package?

Edit: Initial order is looking to be $350 retail...

[breakdirt916]

that's exactly what my air filter was like...gotta love the old bikes that weren't maintained...

$350 isn't such a bad start, and on the plus side, although project bikes cost more in the long run, the cost is spread out over time

did you pass on the plastics?

[Kurlon]

Yup, right now I'm worried about mechanicals first, pretty later.

[Kurlon]

So, before I make a mad order on parts, am I insane thinking 'skip the bushings/etc', do enough to make it roll under it's own power THEN deal with that stuff?

And I don't think the tools I have will let me heli-coil or timesert the failed chain adjuster bolt boss on the swingarm, I don't have anything long enough to work without fouling on the side of the swingarm. Anyone know who could do those repairs without costing crazy amounts?

(And I missed out on a complete set of plastics, with decent gfx for $25 on eBay, sonofa... even my wife is scolding me for missing that one.)

[Paul_E_D]

Which bushings are you skipping? Don't skip the moving parts bushings... i.e. swingarm. You can wear out your frame with that stuff in bad shape, then you have nothing.

I would just tap the swingarm to the next size, or have a local guy do it. Should be cheap, but price a used swingarms at Sky or something.

[gregp]

Check Rocky Mountain, and other places for "repair kits". There were several chain adjuster repair kits offered. They came with a plate that went over the hole, and longer bolts.
Edit: "Swing Arm Buddy" http://www.rockymountainatvmc.com/pr...dFamilyId=2663

It has been quite a while since I have worked on a Yamaha power valve assembly like that one, but IIRC, the pin was used to index the valve to a specific location to ensure proper operation when fully asembled.
To check and clean the power valve components, the cylinder will most likely have to come off.
I have come across many dirt bikes that have components missing and/or mis-assembled, or broken parts. I have also come across some that have had parts from the wrong years installed, which can make a huge difference in operation.

[FTMS]

What size time sert do you need?

[Kurlon]

Hrmmm... doing bushings/bearings/etc, swingarm pivot, exhaust mounts, chain guide, rollers, some gaskets, etc... I'm at $580 retail. That's re-using the old chain, brake pads, and gawdaful plastics/seat/tank/radiators... fug.

Anyone know if Moose's complete gasket kit includes the exhaust gasket and o-ring?

[breakdirt916]

I'll let others chime in on this...

but I'm an ass-backwards brat. I like having the engine in fully functional. Heck, I even rode (well, more flopped around...) at CH with a lower linkage bearing completely destroyed just because the bike ran

But looking back, I'd agree about what Paul said about overlooking parts that will lead to more expensive damage...I had Peter at GMD look at the swing arm pivot, and it looked worn away, but he put it all together and it seems to be ok now.

regardless, I'll join your wife and give you crap for missing that auction. Even though I'm well, well over budget on my bike, I saved over $300 by impulse-purchasing items when they're on ebay or CL and just cheap (new $240 hinson clutch basket for $100, graphics kit for $11, FWW for $20 instead of $140, etc.).

but yeah...I dunno about the heli-coils...I paid PK to fix mine...but I'm 80% sure you can find a local motorcyclists or mechanic through a friend that'll do it for free

but be patient...over time deals will stand out, people will help you out, and eventually it'll come together.