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Thommo_400f

Cam timing .... Help

21 posts in this topic

I decided to check clearances and found that the intake cam was out by 1 tooth clockwise. I assumed it had skipped.

I set it back to Wr... All dots at 9-12-3 on both cams.

Now the power is really odd. Flat bottom - mid and a big hit at WOT.

I'm guessing that all of the jetting I did while intake cam was off by one has messed up my jetting for normal? I'm fairly lean now.

Near sea level 0-300m

160 mj

45 pilot

Fuel screw 1 turn

OBEKP on #1 clip

open air box

Open exhaust

Should I just go back to intake +1 tooth since it was running well with linear power just no hit anywhere. Or re-jet ?

Cheers

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I asked my mechanic and he said that's how they used to set their bikes up.

So I put it back to intake +1 tooth clockwise, exhaust stock and it's like night and day.

Bottom end and mid are so much stronger without losing top end.

Anyway. I'm just going to leave it alone now for fear of screwing something up!

Be nice to understand how it all relates...maybe one day ;)

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Just having a think about it and a bit of searching.

I think there were 13 pins between punch marks which means stock wr timing? Soooo I think my cam chain must be stretched.

I am going to have to take it apart again and double check. :/

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In that picture, your cams are 180 degrees out. Notice how on the Intake cam the "E" is facing towards the carb. We need a different picture with the cams in the proper sequence.

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Yeah. I realized that after I took the photo.

Either way at TDC the cams are symmetrical. And were exactly the same when I rotated to correct position.

I might open it up again tonight.

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Just spoke to my mechanic....it seem I got my wires crossed!

He said that it was definitely 1 tooth out in intake.

He also said that due to the delayed intake opening and closing, it would create a bigger valve overlap causing rich conditions.

I have been combatting rich conditions for a while now and finally leaned it to work well.

So when I switched it back to Normal WR settings...I must have been too lean on the needle for the original setup (it was making a shearing sound as described in the manual) which I guess was why my bottom end dissappeared.

My next move is to put the intake back to normal and put my stock OBDXM needle back in at clip#3 and see if it is better.

Ever feel like you are on a merry-go-round !!!!.

The only good new so far is that my valves are right on bottom end of spec, so no shims required yet.

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Changed timing back to stock WR.

Test conditions:

160 MJ

45 PJ

75 PAJ

ODBXM #3 (was OBEKP #1)

Fuel Screw 1 + 1/2 (was 1/2)

Rode to work

Result:

Start and idle perfect

Chug 1/16 - 1/8 good - no stutters

Mid - seems too lean still so adjusted needle to #5 and will test at lunch

Top end - Very responsive, but I think will be too lean if held wide open for any period (might try 165 main if i get needle right)

I have attached the before and after shots to show how it was 1 tooth out on the Intake cam for anyone who might have same issue ( Jetting suddenly becomes too rich, fouling plugs for no reason)

The beast

Photo 7-09-12 4 22 46 PM.jpg

before

IMG_0795.JPG

after

IMG_0799.JPG

Check out the crap paint job done by previous owner..... time for some paint stripper!

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Dear Diary.......

Well....back to the jetting merry-go-round.

Happy with Pilot circuit, easy start and nice smooth idle.

Moved clip to #5 (OBDXM) and it ran way rich...coughed and sputtered until I got onto Main jet at 3/4 throttle (Main is nice and strong, still pullling hard at 100 kph +).

Think I'll try clip position #1 (OBDXM) and if that is still not right I'll change back to maybe #3 or #4 (OBEKP) needle.

The OBEKP was definitey too lean on clip #1 (no bottom end response and a definite shearing sound) which it was set to when I first found the cam problem and set it to stock..

I'm thinking I went too far by going back to stock ? It's 3 steps difference on straight portion of needle P vs M. A stab in the dark topped with some blind optimism....not the most scientific approach ;)

I'll keep posting progress/fails so you guys can have a good chuckle at my limited knowledge :banghead:

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I put clip on #1 OBDXM

Result:

Pretty damn close.

No stutters

Pretty good mid - almost there

Top end is fine.

Maybe 1 clip position out but near enough for this week. Plus Sick of pulling carb off bike.

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Sounds like you are on the right track.

Ok, so here's the million dollar question: why did it skip? Before spending huge amounts of time getting it right jetting wise, make sure you take care of the issue before it messes with you again.

I'd be thinking came chain is stretched.....may want to put that on your very short list of things to fix.

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Sounds like you are on the right track.

Ok, so here's the million dollar question: why did it skip? Before spending huge amounts of time getting it right jetting wise, make sure you take care of the issue before it messes with you again.

I'd be thinking came chain is stretched.....may want to put that on your very short list of things to fix.

Yep....Totally agree!

I am concerned as to whether it skipped or the previous owner tried to do YZ timing with the wrong cam.

It's difficult to tell simply because the bike was a mess when I got it. Carb 1/2 blocked, plastics damaged, wheel bearings gone, sump plug stripped, swingarm bearings seized, crappy painted engine!

Only after unblocking the carb did I find that it was running way rich. I didn't think at the time that the jetting was so far out that it should point to another problem. Although I doubt I would ever have looked at cams until doing a valve check.

Anyway, I think I'll order a new cam chain and ride it with the current jetting for a while. I think I need a needle between my current DXM and EKP to dial it in but that can wait until I have had some saddle time.

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The interesting thing about the cam timing is that I have found a lot of posts about the same issue.

On 1998-1999 WR400's and 426's there are a lot of photos of the intake cam "looking" 1 tooth clockwise.

My main question is that on all of the WR->YZ instructions they say WR should have 13 pins between top marks and YZ should have 12 when using the stock WR cams.

But my cams when aligned to what seems stock, only have 12 pins between.... :unsure: and the cam timing marks line up perfectly with the head....

Anyone got any opinion on where my cams SHOULD be ?

Cheers

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I've got an 02 426 with a very similar issue. Was running decent before winter, though with some bog off idle, etc. Pulled off carb, rejetted, and found the compression on the kick wasn't what it used to be... Very confused since I didn't mess with anything other than the carb.

Anyway, pulled the valve cover, and found the intake cam to be rotated clockwise one tooth just as you found yours. 13 pins b/w top of cams. As far as I'm aware the bike is bone-stock. No info to help, but you're not the only one there... so TTT!

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The interesting thing about the cam timing is that I have found a lot of posts about the same issue.

On 1998-1999 WR400's and 426's there are a lot of photos of the intake cam "looking" 1 tooth clockwise.

My main question is that on all of the WR->YZ instructions they say WR should have 13 pins between top marks and YZ should have 12 when using the stock WR cams.

But my cams when aligned to what seems stock, only have 12 pins between.... :unsure: and the cam timing marks line up perfectly with the head....

Anyone got any opinion on where my cams SHOULD be ?

Cheers

Well, perhaps the PO purchased the YZ cams and installed them. This would put the timing marks where you currently see them. And about the 12 pins between timing marks. You've got to remember that your supposed to be rotating the Exhaust cam one tooth clockwise to achieve the 1 pin count on the WR cams, not the Intake cam.

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I'm just going to assume someone put yz cams in it and leave it alone. Got bigger fish to fry with this beast.

I am happy to leave everything lined up horizontally since the bike is running ok like that and does seem to have a bit more of a hit at mid throttle and it looks like the picture in the manual.

Thanks for the feedback.

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Will some one please tell me what the timing for wr 426 is ?? 1st time I've ever done this and not sure ...some pics would help cheers

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