Yz426 hotcams?

17 replies to this topic
  • Super426

Posted July 25, 2015 - 01:12 AM


Thinking about doing the hot cams on my 426. Should I do them or the GTYR cams? Bike is already stupid fast but I don't mind more power, as long as I'm not sacrificing any other part of the power band.

  • harmetp

Posted July 25, 2015 - 05:22 AM


I have the hot cam but it was to get the autodecompression feature.  On a track I couldn't say if it's same worse or better, but just running down the road the hotcam seemed to smooth out the power delivery from the stock.  I seem to remember a jump in power with the stock cam (apparently the Japanese test riders still like the 'turbo feel').  Seat of the pants dyno is that it brought the bottom end up.  It's still not a take off from idle bike unless you have a huge rear sprocket.  

  • Super426

Posted July 25, 2015 - 12:24 PM


Ok gotcha. Yeah everyone is telling me not to do it haha

  • grayracer513

Posted July 26, 2015 - 06:08 AM


Everyone is telling you not to use the Hot Cams?  "Everyone" doesn't know what he's talking about.  Adding auto decompression to the 426 is one of the best modifications there is for the bike, and the change to the power curve is is a pretty big improvement, IMO.

  • Super426

Posted July 26, 2015 - 08:48 PM


You have it on your 426?! If it's really worth it I'll do it for sure. I'm just getting a lot of negative feedback on it:(

  • G-BRO

Posted July 27, 2015 - 07:20 AM


You have it on your 426?! If it's really worth it I'll do it for sure. I'm just getting a lot of negative feedback on it:(

I have one on mine. The main added bonus is the starting technique (or lack there of it involves). It's a nice feature, but not a must to a properly tuned bike

  • grayracer513

Posted July 27, 2015 - 03:10 PM


Don't have a 426.  Had one without it, had an '03 450 that came with it, and that completely changed my mind about it.  That bike bump started like a low compression 250.  And of course, my '06 has it, too.


The manual decomp starting drill requires you to find the start of the compression stroke, and then try to figure out how far to move the crank to get to a point where the pist is about two thirds farther up the bore towards top dead center without going past about ten degrees before TDC.  With the auto decomp system, at kicking speeds, the start of the compression stroke is simply delayed until the right spot is reached.  So the difference is that instead of finding compression and going on a kind of invisible Easter egg hunt, you just find compression, raise the kick starter again and kick (you can also just flail away like a two-stroke guy, but my way is more effective).  It's the same drill except you always "find" the perfect spot.


The cams themselves are about as aggressive as the OEM 426 grind, but you will find that where the stock bike has a little flat spot folloed by a surge of power at around 7000  RPM, the Hot Cams pulls smoothly through the range.


"Everyone"'s trouble appears to be that he doesn't want you to have a better bike than him.

  • Super426

Posted July 27, 2015 - 04:55 PM


I don't seem to have that "finding top dead center" issue. I kick my bike about a 1/4-1/2 kick until it hits compression. I pull the lever and kick a 1/8 kick and then ratchet it all the way and kick it once and it starts first one everytime. I actually like having the manual decomp. Makes it really nice for cold starts, and is a good secondary kill switch

  • grayracer513

Posted July 28, 2015 - 06:14 AM


"If you like your manual decomp, you can keep your manual decomp." 


Installing the auto decomp cam doesn't mean you have to get rid of it, but it honestly will not serve too much useful function; you just won't need it for anything very often.


As for cold starts, there is no advantage to having the manual vs. automatic system.  Mine starts in no more than two, usually one kick dead cold.  It's all about the carb and the right priming technique, not the way excess compression is dealt with. 


But I have to tell you that using it as a kill switch, or at any other time that the engine is actually running is a good way to break a valve lifter and damage the head. 


Anyway, you're equivocating, looking for justification for not doing it.  Your choice.  Matters not to me.

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  • Super426

Posted July 28, 2015 - 08:09 AM


I want to do it for the power increase if there is any. To me it's sounds like no one is getting any real power increase and instead just taking out the so called "flat spot" at 7k. I don't seem to have this flat spot.

I love it when people toss out big words and then have to basically add a definition after to help explain the usage they were going for. Ambiguous would have been a better choice my friend;)

  • Super426

Posted July 28, 2015 - 08:17 AM


I don't think everyone understands this post. I want the hotcams but only if they increase power. It's my understanding so far that they only add the auto decompression feature. Something I'm not interesting in buying. If they truly add ponies I'll have them on their way

  • jcm3

Posted July 28, 2015 - 09:16 AM


If you add just the exhaust cam (with the starting benefits), then you'll see a limited performance increase.


Hot Cams claims that with both, you'll see about a 9% increase in power.  I had both in my old YZ426, but these are dirt bikes.  Most of us aren't pushing them to their limits anyway, traction is limited, tracks are different, etc.  I realized when I pulled it apart that I already had a decom exhaust cam.  I did a piston and rings, cams, and cam chain at the same time.  So, it's hard to say what a difference just the cams would have made.


Take it for what it's worth, but 9% is a decent improvement if their claims are accurate.



  • mike_dean

Posted July 28, 2015 - 11:21 AM


Had the hotcams exhaust cam in my 2000 426 since hotcams offered it. Still have the bike no problems runs great. The cam itself probably has 350 hrs on it.

  • grayracer513

Posted July 28, 2015 - 01:34 PM


You could always go to the Stage II level, if power is what you are after.  And, there are plenty of other sources, Webcams, Crower, etc.


Meanwhile, I'll ignore your attempt to denigrate my use of vocabulary, although you should be aware that equivocation and looking for excuses are not synonymous.  Is there a language other than English you would prefer that I use?

  • Super426

Posted July 28, 2015 - 07:58 PM


The two comments before you were very helpful. You on the other hand are the typical forum person. Thanks for making forums a terrible place to ask questions. If you prefer another language we can switch to French. We could also switch to &%$#@!, you seem to be fluent in that;)
Also they don't make a stage two for this bike...:(

  • grayracer513

Posted July 29, 2015 - 06:38 AM


Dropped the stage two, did they?  That's another example of why it's likely to be a frustrating exercise modifying a 426.  They are considered obsolete, and there is very little market support for them.


If you are determined to dump money into it, google up Ron Hamp Cycles.  Ask him where you might find some of the stuff he used to put into them while they were current.  His 5 valve Yamaha engines were at least as powerful (usually more so) as any of his competition's work (he builds Grand National flat track bikes), and I think he finally got one close to 58 HP.  It will be expensive.  But his 5 valve 450's broke the 60 HP barrier. 


You should also understand that while it might be fun to put together and ride, and even if you had a real Ron Hamp 426, the 5 valve head is a limiting factor in the horsepower hunt.  58 was right about the ceiling for a 426, but the '15 with the new 4 valve head and near perfect intake port layout is delivered stock with 57.  A couple of them have already cleared 60 with bolt-on parts, and Hamp thinks he can eventually find 70 in them.


You'd be better off from a practical standpoint to just ride it like it is and move up to something more recent as a bike to build.

  • Super426

Posted July 29, 2015 - 07:36 PM


Yeah I think the cam only helps with the auto decompression... My bike may be a unicorn but it's already wayyyyy faster than a 450. Literally spanks a 450 all day. It must have something done I don't know about. It used to be a factory super cross bike so maybe it has some extra work done

  • flymikemc

Posted August 05, 2015 - 08:04 PM


I put a Hotcams decomp on just the exhaust side and its so much easier to start.  No more process to go through.... just kick and away you go.  Best thing since sliced bread.  Power seems smoother though I think its about the same power.  I might throw in a intake cam just to see if I can grab a little more of that 9% not that it really needs it.  The 98 YZ400 rips!!!

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