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Auto decomp cam update

By adrian,
in YZ400F/426F/450F/450FX

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Rising Star

adrian

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OK this is the biggest smile maker going!! :o?:D:D:D SEE

I cannot believe how easy this mod is(and thats coming from a 2 stroke guy whos scared of working on 4 strokes). I took my time and checked and checked and then checked again to make sure everything was ok and buttoned it all up and one light little kick and brooom she fired up ?

If anyone is considering this mod do it!!!!!! I cannot say enough what a diference it makes, it fires up like a 2 stroke as easy or easier!! Now this weekend I'm taking her out to the track to see how it performs ?

To the originaters of this mod you rule :D??:D

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Experienced

Florida_426

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Adrian,

I could not agree more with your post. My hat is off to Yamaben, Satch and Yamaha.dude (and numerous others I cannot remember the names of) on their work on the modification. That one simple part swap made my 426 so enjoyable. I did not mind the starting drill or the decomp lever but the ease of starting now and the wider, stronger power band have made me a happy old man.

After working with Kirtwell on jetting along with the DCM I have a great running and reliable MX bike for me. I have not had one moments problems with the valves, cam chain or tensioner since the modification. Looks like my 426 will be around for a while now. Doing the little modificatins and adding some bling are icing on the Yamaha cake for me.

Bill

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Grand Master

02YZ426

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Just ordered the Hot Cam decomp for my 426. After discovering this web site and all the hipe about this upgrade, I just couldnt live another day without that cam. I didnt even know there was such a fix out there. If it wasn't for this site, I would have been kickn and cursin my bike all summer.

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Newbie

willy16

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I am new to this site and just finished the cam mod. last week. I also found out obout this mod here. All I can say is O.M.G. I used the factory 450 cam and got lucky not needing to change any shims, just adjust the carb a little bit. I can't thank everybody here enough.

I just started riding again this last year and I was ready to trade the bike this spring because it was such a pain to start when it was hot. That problem is now cured.

Keep an eye on that front wheel or it will jump over your head.? :)

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adrian

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can i do this mod on my yz400f 1998 model? if so i am new to this upgrade and was wondering if anyone has a link or something so i can read about this mod. oh and is there any other easy mods for this bike?

The answer to your question is yes!!!

Go look at the top of the page here for the stickies on the cam upgrade and there is a PDF file that you can download with all the info

good luck,it's worth the time for you to invest in reading ALL of the 19 or so pages on the cam, that way you get a good feel for whats involved,somewhere in there is the link to the PDF file ??

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Explorer

fatnugget

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Add two more successful cam swaps to the growing list. Mine was a '99 YZF400 and my buddies '00 YZF426. I went with the stock 2003 450 cam and he went with the hotcams version. I broke the cam in the other day just on a easy ride around the neighborhood and did notice a nice gain in low end throttle response, very nice and controllable. My buddies bike seemed to like the mod too but he really didn't ride it before we did the mod so it is hard to say how it affected his. We will be going to Moab next week so I will have a lot more time to compare the two. I am sure we will be doing some drag racing just to see who has the faster bike. Plus there is a non-modded '98 YZF 400 so we should be able to get some good comparisons as far as powere goes.

When we were doing the swap on his bike a couple of things I notices was the timing chain really didn't seem to sit down on his sprocket any better than the stock 450 cam. The second thing is that the timing marks on the hotcam cam set his exhaust lobe about 1-2 back or up from the stock cam which I lined up using the pdf file found on thumpertalk. In other words, his cam lobes were closer together while looking at the engine from the side than mine. I think that would mean that his timing would be retarded from mine if I am thinking right it may not really matter on the exhaust side. Any thoughts on the timing? They both seem to start right up and run fine.

On a side note this is the first year we are all going to be on thumpers, when I first bought my bike in '99 I was the only 4 stroke in the group. I guess they are now becoming believers in the 4 strokes.

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Btwick

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Just bought my 450 cam and am planning on the upgrade.. I am a reasonable mechanic but have looked in my manual and on this site and cannot find any information about shimming the cam. Can someone shed a little light on that process such as what tools are needed, and what the steps are..

The rest of the mod seems pretty straight forward with the exception of shimming. Oh , I also get to adjust the valves, something else that I've never done before..

Yamaha will charge me $170 to do the work, which I'd rather not pay..

All help is really appreciated. ?

Thx,

Brian

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Grand Master

TimFurryBalls

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All you need to re-shim and adjust your valves are shims (if needed) and a feeler gauge. If you don't have shims, your dealer may or not have them in stock and will charge you an arm and a leg for them. Buy the Hot Cams shim kit before you begin. You'll never regret it.

To check clearances, look in your manual for a detailed explaination. Or, just find TDC on your cam, and stick in a feeler gauge until it fits nice and snug between the cam lobe and shim bucket.

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adrian

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The dealership out by me is doing an exchange program where I bring in my shims and exchange them for the ones I need. Pretty cool if you ask me!! As TimFurryBalls siad all you need is a feeler guage,pull out the shims before installing new cam and mark down the #s,mine happened to be 178/181 and then measure the shims once the new cam is installed,should be around+-.3mm gap mark, the new shims only go in increments of.5 so in my case I need to go to 180/185... I hope that I am reading the info right and that I have done it correctly hehe, install everything a go riding!!?

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Grand Master

02YZ426

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fatnugget: so the chain didnt fit better with the hotcam? Did you need to do any re-shimming? I was also curious about the timing with the hotcams. Did they not put timing marks on it that line up like the stock cams? Just curious because I just ordered it. I thought that maybe the hotcams was the safer way to go, after reading about the stock 450 cam not being a perfect fit.

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Explorer

fatnugget

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fatnugget: so the chain didn't fit better with the hotcam? Did you need to do any re-shimming? I was also curious about the timing with the hotcams. Did they not put timing marks on it that line up like the stock cams? Just curious because I just ordered it. I thought that maybe the hotcams was the safer way to go, after reading about the stock 450 cam not being a perfect fit.

I didn't seem to fit any better than the stock cam, at least not enough that I would worry about. I did need to reshim both bikes going up about .2 on both machines I needed a 1.95 and a 2.00 he needed a 2.00 and 2.05 but his bike may have had more hours on the motor than mine. There are timing marks on the hotcam that do line up with the stock settings (the dot at 12 o'clock on both intake and exhaust) but it seemed to be different lobe-wise than the stock cam. In other words the hotcam was pointing more toward where the gastank would be while the stock cam would be facing closer to the engine. Does that make sense? Feel free to PM me with any questions you may have. You won't regret the mod at all, I'm loving it so far.

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