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01 YZ426F Hot Cam Questions

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Ok so I'm getting to this update a little late, but I just recently installed the hot cams exhaust cam with auto decompression. I checked valve's. Ran the break in, rechecked valve's, all good there. So here's my question/issue. It started second kick all the time before the change. Now with the Hot Cam I can kick it 5 times it will pop out the exhaust kick it a few more, get a pop then it will start and run. Any thoughts why it's starting tougher now? Could it be as easy as maybe 1 size too large pilot jet after the new cam?

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Do you use your choke when you try and start it? Do you squirt some fuel in with a slight pump of the throttle using the accelerator pump? What size pilot jet are you using? Depending on which pilot jet you are using out of stock or if you are using the stock pilot jet it may be time to upsize it one size or two.  

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Choke on. Ive never done the priming thing before but gave it a try after doing a little looking arond on the site, didnt seem to make a big difference either way. And as far as pilot im pretty sure its a 45. Fresh plug after cam install also.

Edited by Yrider93

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I'm pretty sure that's a stuck jet size. When you change things like a pipe and header or in this case, a performance cam, it has been my experience that starting can be difficult without the proper pilot jet.  I would try a 48 or 50. Assuming your install was done correctly. You might get a size up or two of your other jets for tuning purposes as well as some gaskets for your bowel just in case. The hot cams seemed to have the biggest improvement down low as the stage 1 is all that is available. If there were a stage 2 it would be more on the top end where the cam is more effective. There should be a jetting suggestion for that somewhere on here but my common sense suggestions will likely get you where you need to go.

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Did you reshim the valve clearance? I have had to adjust clearance with a hot cam swap.

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Put it back together and gave it another try, still not starting up very easy. Next thing im going to do is a leak down test to see if anything happened between the time of having the OEM cam in and the Hot cam. Unfortunately I just had surgery so i won't get the leak down done for a few days. Still taking any ideas though lol i really hope i can get it back to starting 2nd or 3rd kick.

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From what I have researched on here, you can't effectively do a compression test on an engine with the decomp cam. So the leak down will give you the results you need to know if rings and valves and such are healthy and sealing.

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Where did you see that :o I’ve done a leak down test on my 426f the other day and once I have it back together today/tomorrow I’m gonna try a compression test (it has hotcams).

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This is one of the few threads that i found. It makes sense, if you think about it the decomp is designed specifically to take away some compression for starting so your compression results will appear low no matter what. 

https://thumpertalk.com/forums/topic/1018454-yz426-compression-test-fried-rings/?tab=comments#comment-10703426

 

Edited by Yrider93

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Have a pic of the cam lobes?
Also check the valves, does the hotcams come with an installation page that has specs? A leak down test sounds like a good idea, not hard to do.
Guess I won't be doing a compression test on my bike or maybe for fun ? 

Edited by Mitch FTB

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I did not grab a pic of the lobes when I was in there just the timing marks, I will get one when i do the leak down test. Valves checked good after the break-in. Although ill be checking again if the leak down has good results

 

Edited by Yrider93

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