Cam Swap Question

Just getting ready to button this up with the new cam and wanted to see if someone would QC my cam timing here. I've got the timing marks in the correct looking 12 and 9 o'clock for exhaust and 12 and 3 o'clock for the intake, with 13 pins between the 12 o'clock marks and the outer marks lined up with the valve cover surface.

0730161706a_HDR.jpg

Only thing now though is the crank TDC mark is a degree or two advanced (left) of where it was with the cams in that position previously. This is the only thing that has me wondering, especially since I did not remove the intake cam during this (there should be no chance the crank would have turned independently of the cam - I didn't touch it).

0730161706_HDR.jpg

I will add that with the stock WR exhaust cam and timing, there were 14 pins between 12 o'clock marks, which wouldn't be possible to make all the marks line up with the head with this YZ cam.

This is the other side - the exhaust cam points up slightly more than the intake.

0730161718_HDR.jpg

The engine spins freely with no hangups.

This is a 2011 WR450 and I'm swapping in a 2006 YZ450 exhaust cam. Thanks for any advice.

Disregard the timing confusion - I think - when I line up the crank timing mark exactly, the cam outer marks are pretty dang close. I'll let everybody know how it goes.

Im not 100% positive but i think with yz cams theres a half link between the two top marks (ie 13 pins) so i think your on good shape. On your crank timing marks did you have 3 lines? If so the last one is tdc on the crank. give me a second to research some pics of my set up and ill let you know

Edited by knuckleduster271

There should be enough slack in the chain even with the tensioner installed that you can line that mark up and your cam marks will still be where there supposed to

Got it put back together - worst part of this job for me is removing the valve cover. I really struggled with the install and finally pulled out the 90 deg breather elbow and it went right on. Also, removing the gasket and placing it on the surface (with a little Yamabond in key areas) and bringing the cover to it and carefully seating it on the gasket is the way to go. Yeah, I'd never even checked the valves on this bike...they are all in the middle of their range at about 125 hrs on the engine.

Anyway, I tried a little experiment with this cam swap and put the YZ cam in as is, with no pin grinding. First start cold on the stand.....it started on the button no problem. It wasn't quite as fast of a start up as with the stock cam, but it did it alright. It actually has a tougher time electric starting when it's hot, not sure why. But it's also noticeably easier to kick. I also had to readjust my fuel screw and idle, that could be part of it. I haven't fooled with it much but it certainly will start on the button with the unmodified YZ exhaust cam.

Here's the visual difference between the decomp pins on the YZ cam (left) and WR cam.

0730161626_HDR.jpg

After you ride it five times using the electric start let us know if you don't have any issues. Prior to changing my pin it would start only some times.

Edited by stevethe

Mine would e-start 20% of the time with my first cam swap.

 

Grinding the pin fixed it

After you ride it five times using the electric start let us know if you don't have any issues. Prior to changing my pin it would start only some times.

Yeah, just got in from the garage - it's tough to get started on the button when it's hot, no doubt. I was trying all sorts of different hot start/accelerator pump blip/throttle setting combinations after running it (by kick start) and clearing it out to see if there's an e-starting ritual that might work. I've gotten it a few times, but not consistently and the battery started losing juice. I'll keep working with it, but I was pleasantly surprised when it started pretty easily on initial start up.

Worst case, I take it back out grind that baby down a little. Probably drop in a YZ or YFZ intake cam while I'm in there. I'd really like to pull the head and do a little home port and polish, but I'm not quite that motivated right now.

The exhaust cam cannot do too much without a big gulp of fuel coming from the intake cam. I think there is more power less risk of loosing torque from just installing the intake cam.

I am currently using a GYTR intake cam only on my 16'

Mine starts easlily hot or cold- I do have to pull the hot start lever- bit that was an issue even before the cam swap

Mine starts easlily hot or cold- I do have to pull the hot start lever- bit that was an issue even before the cam swap

With what cams. I thought your running the Hot Cams.

Im running a hotcam intake and an 06 yz450 exhaust-cam

Im running a hotcam intake and an 06 yz450 exhaust-cam

Ah hah interesting. You must have gotten lucky with that cam in not grinding the pin.

For some reason, I thought the best bang for the buck was the exhaust cam swap, but that might have been a holdover from the pre-'07 WR when the intake cams were the same as the YZ...or so they say. A lot of this stuff is propagated on the interwebs by some people who don't have first hand, accurate knowledge (NOT indicating anyone in this thread, just stuff I've read in the last few years).

But I had to try the unmodified YZ cam install to see if it would work with the button. Now I'll order up an intake cam of some sort and go from there.

Edited by RockerYZWR

My advice is to avoice Hotcams due to quality and cam timing issues

The Hot cam does loose some low end torque on a dirt bike. I have some sitting in a box.

The Hot cam does loose some low end torque on a dirt bike. I have some sitting in a box.

 

 I went through (3) sets of YZ spec in/ex camsets and the third one was timed correctly.

The first two you could see the gear timing marks were at leat 25 degrees off....

 

In the end it was pretty much a flat track only cam, as all it did was give you a 8-10k rpm massive peak, and not much else. 

Nothing like a stock YZ.

There is one other cam from MMAD that does not loose all the torque.

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