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450F cam retrofit
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Posted by: Jonny426---------------------
Ok, the new YZ's&WR's start really easily with the decompressor cams. The debate is all about diameter/width of the cam sprocket and if the difference is great enough to cause extereme cam chain wear. Has anybody here installed one? If so how many miles on it and how is your cam chain holding up? I'm hoping to get Rich to weigh in on this because my buddies' WR450 kicks so nice...
Posted by: Rich Rohrich---------------------
Quote:
Originally posted by Jonny426
I'm hoping to get Rich to weigh in on this
|
I haven't measured the new cam so I can't add anything useful. Sorry.
Posted by: Jonny426---------------------
Thanks Rich. I guess I'll have to volunteer to my buddies' first valve clearance check...
Posted by: DEANSFASTWAY---------------------
Ive done a few of these and they seem to last really good .On a couple of them with a lathe I was shaving a tiny bit off the inside of the 450 sprocket to help center the chain. My latest question (unanswered as of yet) is about 400Fs with steel valves. Im scared to run450 cam without switching over to TI valves. thinking maybe I might see a float problem and dont want to find out the hard way. Anybody been there? Let us know. Thanks DEAN
Posted by: DEANSFASTWAY---------------------
Johnny426;the 426 sprocket is.230in/5.84mms and the 450 sprocket is.246in/6.25mms .The chain seems to fit just fine except that the exh sprocket is like .030in closer to the cam cap on the head this is the alignment issue that everyone is concerned with. On two of these I chucked the exh cam in a lathe andremoved .020in off the inner side ofthe gear teeth just for good alignment. The 426 cam total lift is .319in/8.10mms and the 450s is .324in/8.24mms . Every time I install these 450 cams in 426 I need to change out the usual 1.74 shim for a 2.15or 2.25mm shim to get the valve clearance back up to specs. Funny on the01/02 250Fs It seems like I can always just drop the 03 cam right in . Then you can start the bikes by hand. Wonder what the intake cam for the 450 or Id be curious to see the specs on the Hotcams . If youre changing out a cam in a 426 thats a year old or so Id recommend replacing the Timing Chain anyway . Yamaha chains are cheap but Hondas are like $85-$90 for a XR/TRX 400 . Good Luck
Posted by: Jonny426---------------------
Thanks Deans. The cam is on order,I've just gotta try it.
Posted by: Henrik---------------------
This question has been debated on www.thumpertalk.com, check the thread out on the YZ-forum.
It seems that the 450 cam and the 400/426 has the same pitch and the same number of teeth. This also means that the chain must ride on the same diameter on the 450 as on the 400/426. I haven't done this mod yet, I'm going to later this summer. Reading through the thread at thumpertalk convinced me that there won't be any problem with the conversion (any=sofar alot of people have done it and so far there hasn't been any reports on damage on thumpertalk at least).
I tried looking for forum rules as all forums don't allow you to comment what you read on other forums - if it is not allowed here: Well, I appologize to the moderator, I looked through tha faq and didn't find anything about it :-)
Posted by: Jonny426---------------------
I have read thru the T.T. stuff a couple of times and am still not convinced the swap is the safest, sanest thing to do... Oh well ,the cam is in and shims are on order.
Posted by: Jonny426---------------------
I finally got a few moments to play...The cam offset difference doesn't scare me too much, there is still a bunch of side to side clearance on both sprockets.The bike kicks like my wife's 125L- no more decompressor.I just need some time to ride now, it's been pouring all day....
Posted by: DEANSFASTWAY---------------------
I did a 426 last week and after the cam swaperoo I could start it by hand.
Posted by: BSWIFT---------------------
Just curious, what did you guys pay for the cams?
Posted by: SFO---------------------
Both cams use the same pitch cam chain.
I will have them both in my hands in the next few weeks and will check the gear profiles on the optical comparitor.
I believe the the od is not as critical as the engagement depth, or diameter at engagement depth.
Posted by: Jonny426---------------------
BSWIFT- $,105.00, I am told that's wholesale. SFO I did the first clearance check on my buddies' WR450, as you said the chain pitch looked the same as mine(side by side comparison). The chain doesn't ride into the exhuast sprocket as deeply on either machine so the O.D. measurement is not a good way to determine fit. DEANSFAST brings chain alignment to the table, but again there is so much side play on the 426 intake sprocket I don't see a problem. On my 426 the new cam is more out of alignment on the outside edge,not the inside. Maybe Yamaha was sloppy on their cam bearing retainer grove spec/machining?
I finally got a chace to rip it up a little last nite. bike still starts 1-2 kicks warm w/o hot start most of the time.It seems to have a smoother mid hit and pulls well nearly all the way to the top,but not as stronglynear the rev limiter. I recently installed the GYT-R insert so that is likly the difference in top end pull. It is quiet enough for most any riding spot,and runs better than my stock vortip did.
Posted by: SFO---------------------
The machinists handbook has a section on how to gauge the gear profile on silent chain sprockets.
If a pin that is .75 of the chain pitch (.25") is laid in adjacent teeth you can measure the base circle profile.
So, If you take a .187" pin and lay it in the opposing teeth of the sprocket you can spot the O.D. at the pins and subtract the dia. of one of the pins to get the true base circle of the sprocket.
Silent chains are really neat and it has been fun researching them.... :thumb:
Posted by: DEANSFASTWAY---------------------
Johnny 426 did you have to reshim?
Posted by: Jonny426---------------------
Yes I had #172® shims stock, so I went with 195's. I could get away with a #200 on the right valve but it would be really close on the left, so i'm playing it safe for now/ recheck in a couple of weeks.
Posted by: Trailgage---------------------
I am planning on putting the "WR"450 cam in my 2000 YZ426. I have seen a lot of info on retrofitting the YZ cams but I haven't seen anything on the WR450 cam.
Does anyone have any idea what the differences are between the YZ450 and the WR450 exhaust cams. They have different part numbers on the Yamaha website so I am courious.
I ride my YZ in enduros and have riden a 2003 WR450. I was so impressed with the WR's ability to lug at low rpm without stalling that I ordered a WR cam for my 426.
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