Having problems with HotCams. (Tuning??)

Well, i dont mean the HotCams set is ruining something because i still believe that i have just a tuning problem.

I installed a set of these cams a few weeks ago together with a Wiseco high compression piston. I took the bike for a spin on the pavement and noticed a slightly engine failure wich i posted the story here in this fórum, for some of you who might remember.

I had to store the bike again after that short spin due to the lack of time to ride it.

Anyway, this Sunday i started the bike (allways starts easely) and prepared myself for an off-road ride. I left home alone heading for the dirt tracks and was riding only with 1/4 throtlle to let the engine warm-up.

When i decided to open the rest of the throtlle the engine started to fail and also backfired constantly...looked like when we are running out of gas.

This happened at 1/2 throtlle and didnt let the engine to achieve higher revs. Also, the engine now makes a lot of valve noise at medium revs, doenst make this noise at low or high revs.

I decided it was better for me to head home but suddenly the engine went OK. It was very strong in low end and i even noticed the wild top end power out of the 426cc but the valve noise was still there. I kept my riding plans untill i stopped the bike to drink some water and to cool down a bit. The engine was off for like 15 minutes. When i started it again, easely i must say and with stock idlle, it made the same thing again...didnt wanted to go over the 6.000rpm(aprox.) mark. Started to backfire and loosing power but allways with perfect idlle capabilities, never shuting off. This problem again went away after 1 or 2 minutes rirding, then everything looked OK again.

The cams are aligned like the factory set and i didnt modify the HotCams cam gear geometry. The valve lash is tuned with the same settings as the original lash would be but the valve noise coming from the head area makes me think something is wrong.

I e-mailed HotCams but still waiting for the answer. There is a member here wich has the nick "HotCams", dont know if he has nothing to do with the HC guys.

I just wrote this stuff hopping for some opinions of someone that might experienced anything similar to this.

Thanks for your time.


Did you check the cam chain tensioner?

Did you gap the rings?


I'll second that !! :):D :D :D


Did you check the cam chain tensioner?

Did you gap the rings?

Every one of those items are for sure in good condition and well assembled. Also, in the HotCams site, they say that the valve lash can have the same setings as OEM. I must say weird too :)

With the noise in the top end, check to be sure the cam chain is tight. The plunger on the tensioner may not have released.

Sounds like the cams and piston have effected the jetting a bit. Seems to run fine but only after a very long warmup. Same thing happened to me when I changed to YZ timing. Raised the needle one clip and it runs fine.

Sounds to me like something in the carb. When a cam fails, it won't suddenly come back. Fuel flow will do that though. Maybe something in the main jet well of the carb. I'd take the carb off and it give it a thorough clean job and blow it out with compressed air. Make sure the jets are all tight.


Sounds to me like something in the carb. When a cam fails, it won't suddenly come back. Fuel flow will do that though.

Good point.

Your cam timing is OFF, RECHECK IT.

Your cam timing is OFF, RECHECK IT.

How can it be off?? Everything is perfectly aligned. I once had an experience with a wrong cam timing...the engine backfires when you release the throtlle and its hard to start when hot. My engine runs OK in every situation and starts easely except for that detail that has developed now at medium revs. I`ll check my carb and if i dont find nothing wrong i will try to change my needle clip position.

But i am still worried about the head area noise :)

I beleieve that hot cams now ships their cams "pretimed" but as a rule of thumb I always use a degree wheel to double check everything.

The Hc's are indexable via slotted cam gears.

That sure sounds like cam timing to me. I spun an intake cam this summer, like 15 degrees. It ran exactly as you describe. It would cough and sputter on top for a while before finially clearing out and running fine. Let it cool off and it would do the same thing all over again.

Even with the timing off this far it would still start fine and idle. Although the idle was a little funky. Suprising I never smacked a valve.

This is what the stock cams should look like when timed properly.


And this is what they look like when the cam gear has spun.


Yzman...i must say thumbs up :) to your help here, with pics and all. Finally i found a member wich had a similar problem. I can swear by God that all my engine parts are well assembled and the valve lash is the correct one. I have been knocking my head all over the place these past days when this happened. I can only go for one theory...

There is a strong possibility that the Wiseco piston is making contact with the valves, i dont believe all of them but maybe a few. This kind of contact is not enough to damage a valve but maybe when the piston is comming up to for the exhaust stroke, he can touch the exhaust valves before the springs can bring them up or even touch the intake valves in the same stroke due to the intake cam is opening the intake stroke too soon.

Its a possibility...its something for the engine masters to comment :D

Please help...i want my engine back :D


Anouther way to check to see if a sprocket has spun on a Hot Cam is to look at the paint marks. There are the three marks on the outside of the gear, and there is a forth mark that goes from the center of the cam to the gear, just for this purpose. If that center mark does not line up then we know that it has spun. Keep us posted with what you find. :)

Its my understanding that when the motor is at TDC and all the gear mark's line up corectly that the cam lobe centerlines are 115 degrees from max lift. Meaning as far as I can tell that if you were to make a line from the tip of the cam lobe to the center of the cam that this line would be about 15 degrees up from horizontal. Assuming that Max lift is when the cam lobe is pointed straight down.

Does that make any sence??

It took me a long time to figure out that my cam gear had spun. My dealer couldn't even figure out that one. I finially figured out that it was supposed to look like pict #1 not #2. I ended up timing it by eye and forgot the marks to get it closer to Pic #1. It ran much better. This told me that I had a problem. I replaced the cam and had the gears welded in place to prevent further slipage.

There is probably alot of things that could be causing your problem. This is just one of them. But its worth a look at. Most people, me included, just look at the gear markes and call it good. While never looking at the cam lobe positions.

Good Replies Donny! :D I would have never thought the gear could spin relative to the cam lobes. Learn something new everday on TT. :)

I found what was causing the engine failure...an iridium spark plug. It was new when i installed the cams...dont know why the bi"#% gave up sparking...anyway i installed a normal spark plug (the original one) and the bike is great now.

Such a head scratching just for a blown plug :):D

Sometimes the most obvious things are the most easily overlooked.

Glad you got it running.

Im glad you got it figured out too! I hope you didnt have to tear it down, just to find a bad plug.

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