Sign in to follow this  
Followers 0
Krannie McKranface

YZ cams

52 posts in this topic

You starting to like that WR more than the X?

Not yet.

The X still KICKS IT ASS, but weighs and feels so much more heavy, that it wears me out.

I still have about a dozen little adjustments to make so it will fit me better (even taller seat, different bar bend for my bad shoulders, etc)

I'm having carb troubles now: the accelerator pump stopped squirting hard, and I think the new cams want a bigger main: I have a 168 now, and I'm gonna try a 175.

It's all apart again already....

Share this post


Link to post
Share on other sites

Yeah, the main jet is waaay to small. Gonna go to a 180! ....and replace the emulsion tube, and the apump linkage rod: it appears to be shorter on this WR for some reason, so when I changed to the short rivet diaphragm, it does not push down the diaphragm far enough to make a good squirt !! Never seen that before....

Share this post


Link to post
Share on other sites

Yeah, the main jet is waaay to small. Gonna go to a 180! ....and replace the emulsion tube, and the apump linkage rod: it appears to be shorter on this WR for some reason, so when I changed to the short rivet diaphragm, it does not push down the diaphragm far enough to make a good squirt !! Never seen that before....

Can you measure overall length of the rod?

I am getting ready to install the short rivet diaphragm along with the R&D power bowl II and do not want to have the same issues.

Share this post


Link to post
Share on other sites

Can you measure overall length of the rod?

I am getting ready to install the short rivet diaphragm along with the R&D power bowl II and do not want to have the same issues.

I'll know more on Friday

Share this post


Link to post
Share on other sites

I have the YZ exhaust cam in my '03 WR, but I'm still running stock jets I believe, what jets do you guys recommend?

Share this post


Link to post
Share on other sites

Any update on this?

Thanks!!!

Yes, yes, sorry.

The rod is fine. All FCR MX 39-41 have exactly the same rod.

We found MY problem: the check valve in the apump cover was not working.

I am driving to Norwalk tomorrow (it's good to be the King) to get a replacement.

What was happening, is the pressure of the rod on the diaphargm was being compromised by a leak on the other side of the diaphragm, dropping the squirt pressure down to almost nothing.

There is a check valve in the cover to prevent this (it''s in the bowl on the stock version) that is supposed to slam shut as soon as the diaphragm starts to move down.......but it didn't.

We put the stock bowl and cover back on the carb and had a 6' squirt !

Then with the R&D set up, we had a 2" squirt....Es Muy No Bueno.

Hense, the RADICAL flat spots in throttle response.

I use the R&D Powerbowl II on bikes that get dual sported, as it really improves partial and steady throttle repsonse quality.

It's not a 'must-have' upgrade, unless you are like me: OCD+Anal+a really good job

All should be better tomorrow.

Share this post


Link to post
Share on other sites

Then with the R&D set up, we had a 2" squirt....Es Muy No Bueno.

Wow that sucks!

I am sure you are getting real good at taking the carb off the aluminum frame WR’s.

What did R&D have to say about the issue? Is this a common problem they have with the PowerBowl II ac pump cover? I looked at mine and it looks like once the check valve is put in there is really no easy way to remove it clean it out or even check to ensure it is working correctly.

Share this post


Link to post
Share on other sites

Wow that sucks!

I am sure you are getting real good at taking the carb off the aluminum frame WR’s.

What did R&D have to say about the issue? Is this a common problem they have with the PowerBowl II ac pump cover? I looked at mine and it looks like once the check valve is put in there is really no easy way to remove it clean it out or even check to ensure it is working correctly.

So, it works now (off the bike).

Getting some Power Now Plus wings to try in the Carb, so the bike will reassemble tonight or tomorrow.

Normally I don't like 'carb jewlery' but I wanted to try it on this bike, cause it will see a lot of 35-40mph street riding.

Share this post


Link to post
Share on other sites

So, it works now (off the bike).

Getting some Power Now Plus wings to try in the Carb, so the bike will reassemble tonight or tomorrow.

Normally I don't like 'carb jewlery' but I wanted to try it on this bike, cause it will see a lot of 35-40mph street riding.

I will be there tomorrow at 9:00 (well, there being not at your house, but there). You could always stop by and help. :busted:

Edited by kenshaw720

Share this post


Link to post
Share on other sites

I will be there tomorrow at 9:00 (well, there being not at your house, but there). You could always stop by and help. :busted:

I'll be sure to bring my own tools

AK9113.jpg

1 person likes this

Share this post


Link to post
Share on other sites

Well, it's becoming a real issue with these YZ Hot Cams for the WR.

Ken may want to tell his own story, but the the bottom line is that his Exhaust cam decomp pin does not stick out far enough to work. It's 1mm too short!

Kicking and e-start reveal way to much compression.

We confirmed this by comparing with the stock cam. So his cam is going back to Hot Cams for a replacement.

My HotCams exhaust cam works fine for e-start............

My 'bog' issues have turned out to NOT to be carb related.

The carb bench tested perfectly, but once it was back on, the big flat spot was still there.

I rode Kens' bike before pulling out the Exhaust cam, and his runs better, and has a better powerband than mine. Quite a bit more linear power in the low and midrange.

Our two bikes are not identicle, but I cannot see the differences accounting for the huge difference in powerbands.

The differences (Krannie vs Ken)

Dr D vs Yosh exhaust

NCVS vs JD Red Needle

12.3:1 vs 12.5:1 piston (both brand new complete top ends...)

Other than that both bikes are the same, with the gray wire cut, no TPS, HotCams YZ cams, main/pilot, etc, etc.

But Kens' runs with a normal power band, nice and linear, predictable, and it feels great.

Mine runs and idles fine, but has a major flat spot through the midrange, then a MASSIVE hit right before it signs off.

Here is my highly scientific SOTP Dyno chart:

IMG_2280.JPG

If I didn't know any better, I'd say that the cam chain gear on my cam was never timed, and that I have a mess of a cam set up.......

I can't see how his SHORTER header would make broader power than my LONGER header, and a bump of .2 in the compression surely would not make that kind of difference.

I can only assume at this time that my HotCams cam is also defective....

I'm just not sure anymore! I'm anxious to put back in my stock cams to see what happens......but WHAT A PAIN in the ass.....

Edited by Krannie

Share this post


Link to post
Share on other sites

I will post up the pictures of the stock cam and the Hotcam tomorrow. They will show the difference between the decomp pins. As Bill said, this is becoming frustrating.

When are you gonna put your stock cams back in? Wanna trade Hotcams? :-). Make sure to take pictures of your Hotcam to see if there is a difference and note the part number stamped on the cam.

Has anyone else had an experience with these cams?

Share this post


Link to post
Share on other sites

I spoke with a couple of motor builders, and the conscience for my power band trouble is that the cams have not been 'degree-ed' to the cam chain gear attached to the cam.

It's like this, oversimplified:

If the position of each cam lobe, pointing straight up, they have to be in a relationship that makes them open/close the valves at a position on the crank that has some minor degree of overlap between the intake and exhaust lobe positioning, relative to the crank.

The more over lap, the more high rpm you have.

The less overlap, the more low end rpm you have.

The WR is delivered with less overlap on purpose, to tame the power.

Hence when you retard a stock WR cam by 1 tooth, you are changing the relationship of the two cams by 22.5 degrees : you are increasing overlap to gain more top end.

If the Hot cams come shipped without the degree timing relationship of the gear to the cam lobes not set, then you get 'pot luck' when you install the cam.

So, if I degree the cam, I should solve my 'flat spot' problem.

Share this post


Link to post
Share on other sites

Is that what you are going to try? Won't that now through off your e-start as it will adjust the timing when the decomp pin hits to release the compression when trying to start it. Or are you talking about unscrewing the gear and rotating it a tooth on the cam?

Either way, if you have the cam out, take a picture and measure the decomp pin length.

Edited by kenshaw720

Share this post


Link to post
Share on other sites

Ok, so here are some pictures of the stock cam and it's decomp pin and the Hotcam and it's decomp pin:

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0