HotCam install question

[Barta001]

Long time reader, first time poster. Thanks to everyone for their contributions to this forum.

I'm installing a HotCam exhaust cam in my '00 426. I've searched the forum but can find an answer specific to hotcams and number of teeth between dots.

I did find that when using original parts there should be 12 teeth between the top dots. There were 12 when I took the old one out.

I also found that when using the 450 cam there should be 14 teeth between top dots.

I didnt find how many or if it matters when using the HotCam. It seems to line up best with 13 teeth between top dots. I can call hotcams tomorrow to see what they suggest but I thought I'd ask here as well. I know lots of people here have installed it so someone's gotta have an opinion.

Thanks

Barta

[grayracer513]

To start with, counting pins between timing marks is not the correct method of doing cams originally intended to be installed in a 426. It's useful as a cross check, but that's it.

Line up the three timing marks (one on the crank, one on each cam) as shown in the manual. On a 426, with cams marked for the 426, you will find 13 pins between the two marks at 12:00 on each cam. That's what you should have had when you took it apart, unless you have a WR that someone had reset the timing to YZ specs.

[Barta001]

Thanks Gary!

[grayracer513]

Thanks Gary!

¿Who?

[beaver83]

HotCams camshafts are designed to have the same timing setups as the stock cams. once in a while they are not quite perfect, but for the most part they are going to be the same as stock cams for timing purposes.

[grayracer513]

...once in a while (the timing marks) are not quite perfect, ...

This is true of OEM cams as well, and it has as much to do with chain wear, and the length of the run of chain running up from the crank as anything else. It's not at all uncommon for the cam sprockets to fail at lining up "perfectly". The question the one must ask is whether moving the cam one tooth in either direction will improve the alignment, or make it worse. In extreme cases, this is where using the inter-sprocket pin count can be useful. That count is normally 13 pins for all YZ400/426/450's except 400/426 engines using a cam made for a 450.

[Barta001]

Grayracer513, sorry for calling you Gary. I have seen many of your posts and for some reason, my brain was always seeing Garyracer513 instead of Grayracer513. Then I assumed your name was Gary. I know what assuming does....

I did use the steps listed in the manual when installing the new cam but it didnt mention number of teeth. Probably beause like you said, its more for cross checking. I remembered reading 12 teeth should be between the marks but 13 seemed to line up better. After you said that there should be 13 I was glad because that lined up the best using 13. I went back and found the article that I was looking at that stated 12 teeth was for a yz250f.

I got it all back together but it was too late to attempt to start it. I'll be out of town until Sunday so I'll post back how it goes then.

Again, thanks for your help!

[grayracer513]

I did use the steps listed in the manual when installing the new cam but it didnt mention number of teeth. Probably beause like you said, its more for cross checking. ...I went back and found the article that I was looking at that stated 12 teeth was for a yz250f.

True, the manual never mentions the count between sprockets. It's only through technical folklore that it gets mentioned. It's important when using an OEM Yamaha 450 cam in a 426, because the timing marks on that cam don't align with the older head. It also used to be used before auto decompression to alter the timing of a WR to YZ specs, or vice versa. But cams need to be in time with the crank. If each of them are, they will naturally be in time with each other.

You may find the bike starts differently. Several times, I have seen posts where people install AD cams and then have trouble starting them. Part of it has to do with the engine itself. Sometimes, the change will cause the bike to like the throttle just tipped open a bit above an idle when it's cold, other times not.

Another error AD newbies make is in thinking they need to take the engine over TDC. The correct way to set up for a start is to push the piston up against compression as you used to, then reset the starter lever to the top of it's stroke and kick it from there. Taking it over the top is a nuisance, and makes it harder to start.

[jayh300]

AD newbies..... I was there.

Mine was a 99 yz400f, but as gray said, in my case, my bike did start different after the cam install. Before I started the bike with my had on the brake m/c. After it actually liked a blip or two of throttle, then held open just a bit. the cool thing is it will bump start easy if you "happen" to shut it off like I used to alot. Once mine was warmed up, it did not matter where you kicked it from. Cold as gray said worked perfect.

[grayracer513]

...the cool thing is it will bump start easy if you "happen" to shut it off like I used to alot.

That is an endearing feature of the conversion, isn't it? With AD, they bump start like a 125 (a very heavy 125)

[jayh300]

That is an endearing feature of the conversion, isn't it? With AD, they bump start like a 125 (a very heavy 125)

correct sir.... the first time i stalled it, after the install, I was coasting to a stop and realized....... dump the clutch dummy....fired right off.

oh yeah a 260lb 125....

[roberts189]

Hey I have a wr426 but stil hav the manual decomp lever and am considering changing the exhaust cam to get the auto decomp but was jus wondering how much difference it actualy made when you done it?? Was it worth it??

Would you recommend changing the inlet cam while im there as well and what cam is best to replace it with Ive heard the best 1 to change to, so not to have to mess about to much with timing, is a post 03 wr 450?? but im contemplatin hotcams, and I come accross this step by step video that mite be of interest: http://www.hotcamsinc.com/index.cfm?fuseaction=cInstallationVideos.viewInstallationVideos

[grayracer513]

How much difference in what regard?

Yes it was worth it.

If you use an aftermarket cam, then you can choose between one made as a WR cam, or a YZ cam, and use the timing marks just as with the stock cams. If you use an OEM cam from an '03, whether it was originally for a YZ or a WR, you will have to use the timing procedure laid out in the thread on the subject in Common Threads (see the forum index).

The only difference in a WR and YZ cam timing originally was the timing of the exhaust cam; the intakes are both the same. Thus, if you put a YZ exhaust cam in a WR, it essentially had YZ cam timing.

If using aftermarket cams, and staying at the stage one level for either a YZ or WR, there is little advantage to replacing the intake. Changing to a YZ exhaust cam is worth 2-4 hp, but it gives up a little of the low speed smoothness of the WR.

[roberts189]

Sorry, I meant how much easier did it make to start? But I didnt realise that there was more power gain from a YZ cam to a hotcam, is there any websites people know of that are good to get tings like this from or is it just a case of waiting for one to come up on ebay??

[grayracer513]

Sorry, I meant how much easier did it make to start?

It won't change anything about how willing the bike is to start, as far as the carb and spark are concerned. It will still be a little fussy. But there's no more "drill" involved. Just punch it up against compression, draw back and kick it. Or, just kick it.

But I didnt realise that there was more power gain from a YZ cam to a hotcam,

There isn't, at least not from a YZ to a stage one Hotcams. But there is when going from a WR to either the YZ or the stage one for the YZ.

[Barta001]

It won't change anything about how willing the bike is to start, as far as the carb and spark are concerned. It will still be a little fussy. But there's no more "drill" involved.

Its true, it started on the 3 kick! I was able to ride on Tuesday evening to break it in. It works like advertised even though my fingers kept reaching for the decomp lever which was no longer there.?

Thanks for the info GrayRacer!

[roberts189]

Yeh I think being able to kick it without the leaver would make things easier, did you just take your leaver off when you installed the new cam? because mine is part of the clutch leaver.

Wot is the break in proceadure, jus take it easy for a cupla hours??

Thanx for the info

[tmc55]

i have 1 question i have a 2000 yz 426f witch auto decomp exhaust cam would be better for me the oem cam or the hot cam thanks

[Barta001]

Wot is the break in proceadure, jus take it easy for a cupla hours??

From the HotCam Instructions:

"Upon initial start up it is very important you DO NOT let the engine idle. We suggest running the engine for at least 30 minutes of run time, at 3000 rpm or better. We recommend a light trail ride to maintain the engine RPM above 3000 rpm. Only light engine loads are to be used. No excessive rpm or lugging. Let the engine cool, Check you valve clearances again with the entire engine at room temperature."