650R stage 1 cam???


4 replies to this topic
  • pchansen

Posted October 01, 2005 - 07:35 PM

#1

I know this has been beaten to death and yes, I've done a little bit of research but I still have two questions regarding the switch from stock to stage 1. What exactly will I be loosing when I forfeit my auto-decompressor? Is it just that it would no longer be a good idea to start the bike with my flip-flops on? :lol: Second, a guy I met at the local track (Washougal- and yes I run the BRP at Washougal on practice days and surprise alot of people when I pass the on one of the table-tops) anyway, he said he had changed to the stage 1 cam with great results but needed to take the bike to a local shop for installation because the cam had to be "pressed" in. Looking at my service manual, I see no procedure for pressing anything in and to me it looks like about a two hour DIY job. BTW, I mostly ride ORV trails here in Washington state, which by the way are like a German Virgin....Goot-und-tight!! :banghead: :applause:

  • qadsan

Posted October 01, 2005 - 08:45 PM

#2

The auto decompressor mainly does two things when its working properly. The first thing an auto decomp mechanism does supposed is it makes kicking the bike over easier by bleeding off a little bit of compression when you kick it over. With the Yamaha YZF/WRF bikes, you can definitely tell a difference in the kick when starting a bike with or without the auto decomp mechanism. I don't see much difference in ease of kicking down the lever with the 650r's with or without the auto-decomp mechanism, so it can't be bleeding off too much pressure on this bike. To me, my bikes start as easy as they did before. The second thing it does is it prevents the kick start lever from kicking back at you should the engine rotate backwards for any reason while trying to kick it over. It does this by temporarily openeing one of the exhaust valves should the engine spin backwards for any reason. If you always start your bike with a kick with a full kick from just past TDC, you won't have any problems. If you stab your kick start lever quickly or from any old position, then there's a small chance your kick start lever will kick back at you and without the auto decomp mechanism to bleed off pressure, the kick back could be mild or wild. In fact, I've talked with a XR400 rider who kicked his bike quickly from any position like a 2 stroke and his lever kicked back so hard that it broke off and the lever's shaft stabbed into his leg (ouch!).

The cam does not need to be pressed in. It simply bolts into place, but you will need to pull your old cam gear off and press it onto the new cam and that requires tools (puller & press). You can also simply buy a new cam gear and screw from Honda for something like $30 and new cam gears often slide right onto the end of the cam without any troubles and that will save you some hassle if you don't want to pull the old cam gear off. If you do pull the old cam gear off, you'll see it has two ears on where bolts pass through and if you use a puller on those ears like I've seen done by other people, then there's a good chance you'll break those ears off and then you'll need a new cam gear.

If you've never installed a cam in a bike before, then give yourself a full morning or afternoon just so you're not pressed for time. It's really not that hard to do and you'll be smiling a bit more on your first ride. The valve cover is sealed with a large rubber gasket and you'll need to clean that up and use some non hardening sealant on it when you put it back together, so make sure you have some HondaBond or YamaBond or 3Bond on hand to do this. It's sold by the tube and one tube is plenty for doing a lot of bikes. 3Bond makes this stuff for Honda, Yamaha, Kawi, etc, and it's all the same stuff that's marketed under the different brand names. The 3Bond brand is usually the cheapest and as I recall, YamaBond was priced less than HondaBond even though they're the exact same product, all of which are made by 3Bond.

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  • pchansen

Posted October 02, 2005 - 06:34 AM

#3

Thanks Qadsan! I can always count on you for the last definitive word on the BRP! Would you recommend the HRC cam or XR's only version or whatever? Is there a difference in profiles from on vendor to another?
Thanks again!
Paul

  • qadsan

Posted October 02, 2005 - 07:46 AM

#4

If you get the XR's Only cam, you may need to have your rockers hard welded to match the surface hardness of the cam. You'll have to check with them to see if their cam is hard welded and if so, then you'll need your rockers done and you may need new valve springs. If by chance you're also going to use a new piston, then you'll need to clay check your piston to valve clearances just to be safe. If you go with the actual HRC cam from Honda, then you 'can' install your auto decomp mechanism onto this cam. I believe you'll need to buy the matching valve springs, cam gear and possibly the cam chain for this setup, but it's a nice way to go if you don't mind spending the money because it's a lot more expensive than an afermarket cam. The HotCams are one piece machined billet pieces that are about the same hardness as the stock cam, so you don't need the hard welding. For the stock piston, I like the performance of the stage 1 HotCam for general purpose riding. If I was motarding the bike, I'd be going to the stage II. If I was installing a high comp piston, I'd probably install the stage II cam and wouldn't worry about any losses down low as the high comp piston should make up for that and possibly more. The stage 1 HotCams as I recall is a similar copy of Honda's HRC cam in terms of its profile.

  • pchansen

Posted October 02, 2005 - 09:14 PM

#5

It sounds like the Stage I Hot Cam is for me. I checked with Service Honda and a new cam sprocket is $18. Hard welding the rockers sounds like it may be out of the scope and budget of what I'm trying to accomplish- which is just a plug-and-play mod with the goal being a little more of a mid range punch. Although we all know power is like a drug and I'm sure I'll be back asking you questions about the 680 kit with a stage II cam shortly!
Thanks again for all the advice.
Paul





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