Cam timing 426, method of assembly advice?

Hi all, when re-assembling my cams after a rebuild i've come across a slight timing issue and need some clarification on the correct tecnique of timing them? I have read and read all over these forums but cannot find a solution to my problem which is:-

after setting TDC using the alignment mark on the crank whilst the tensioner is slackened off, i can't for the life of me manage to get the timing marks on the inlet cam to stay at 3 o'clock, inline with the rim of the head as it's pictured in the manual. when i release the tensioner, it will pull the inlet cam slightly clockwise, retarding the timing? I have tried and tried several times but no matter which method i use, (cam chain on the exhaust cam first; chain on inlet cam first; set chain 1 tooth off so when tensioner is released it should tighten it into alignment; no matter which way i try i can't get it to stay at the correct timing so that i have 9-12-3 both cams and H "I" aligned perfectly? I am beginning to wonder if my chain is stretched and in need of a replacement? i hope not, as i priced up a flywheel puller from Yamaha today and they want over £120 for one! mental prices or what for a tool that'll be used maybe once a year! :lol: (Unless any of you guys know of an alternative one i could buy? i've had a look at car ones but they seem way too large?)

anyway, back to my chain issue.... it does stand to reason that if the cams were aligned with a slackened chain, then surely when tension was applied to it, it would move in a clockwise direction against the tensioner subsequently setting the camshafts out of their correct timing, granted, only a little, but at high revs this could possibly upset the tuning? :banghead:

Am i being overly cautious here and just set them as close to alignment as possible or is there a problem with a slack chain, which i don't imagine would cause this as a new chain would be "pulled" offline just the same once tension was applied to it, surely? :banghead:

any ideas anyone?

i'd greatly appreciate any tips on where i can get a suitable flywheel puller as i'd prefer to put a new chain/guides on while the engines stripped, even though they seem ok? coz it's a right B@#t@#d fitting the chain over the cogs on the cams, so it don't feel like it's overly stretched?

I know about the 13=WR, 12=YZ links timing thing too, which i'll get around to once i am clear on this alignment issue?

I have a pic in my garage of mine that I took of it just before I disassembled it. Mine didn't line up 100% either. Mine was quite fine being just a little off and it was even better when I went back and advanced the exhaust cam 1 degree setting it up as a YZ. Hope this helps.

yeh thanks for your input. i re-assembled the bike today and the closest i could get the cams lined up (according to the manual) was, inlet cam ended up slightly out, if we're thinking of a clockface, the markings 9-12-3 oclock etc with the 3 being "flush" with the top of the cylinder head, then mine ended up about 2 mm below but not enough to warrant turning the cam back a tooth as then it ends up with the "12" being off which looks more like 11.30. hope you can understand this pretty poor explanation, i think you should get the picture tho?

Anyway, i've decided to leave it as is and assume this "play" is down to the chain maybe being stretched and without a Flywheel puller it'll have to wait a while before i can fit a new one. I don't think the Cam timing is off so much that'll affect the valves travel as it's only "marginally" off? I have 12 links between the cams "12" markings so it's set to YZ timing also. Hopefully there'll be no problems at these positions? will let you know. hope to get her ready to ride for sunday? I am interested to know how it'll perform on the YZ timing too? she was pretty nifty before but could always do with more grunt.( the day we say we have too much grunt, is the day we should give up riding!) :banghead:

It seems that not many people found this topic interesting enough to reply to, or they're totally confused and can't understand what i'm on about?

The whole reason for my asking in the first place was; after having tuned several twin cam Fords years ago i was made aware that the precise timing of the cams was paramount to performance, hence the introduction of the after-market Vernier adjustable camshafts. Precise timing could be achieved even if there was wear in the drive chain by a slackening of the locking wheel, each cam could be rotated slightly in either direction, achieving precision timing on the strobe etc... It just seems strange to me that with the layout of the cams in the YZF/WR engines, there's a lack of range in which to adjust the timing and is a kind of "hit or miss" affair to try and achieve perfect timing? yet so much emphasis was put into gaining as much "trainable" HP as possible when they were being developed in the factory? surely they've overlooked the performance gains that can be had from precise camshaft timing. Maybe an after-market cam manufacturer like Hotcams may introduce a vernier adjustable wheel on their products so no more fiddling around lifting cams out unnecessarily when trying to set precise alignment or maybe there's not significant power gains to warrant producing them?

I for one would gladly pay the extra wad to have "easy" adjustable cams and have the capability of some extra fine tuning, as it may not give extra horses but it'll certainly give extra performance. :banghead:


Forgot to mention Hambone; when you say you "advanced" the exhaust cam by one degree clockwise making it YZ timing. surely this is retarding it? as the rotation of the cams is anti-clockwise and the lobes would effectively be pulled further away from contact with the buckets when cam turned clockwise, hence delaying (retarding) the timing of the valve opening?

I hate to sound pedantic, but i have read that quote several times now on lots of posts on the WR to YZ timing mod, and loads of people were saying "advanced" instead of retarded and at one stage i was even getting confused :banghead:

Thanks for your input anyway, nice to see someones interested :banghead:

Silly me, i just been to the Hotcams site and their exhaust cam without the auto-decompress has the adjustable wheel... cool :banghead:

Actually the question you posed regarding the "advanced/retarded" of the timing chain has got me thinking. I'm going to have to double check for myself to make sure I'm speaking correctly. If you do end up swapping out the cam please let me know, I'd be very curious how it goes. When I moded mine to the YZ I was tremendously pleased with the performance increase!

hi, i looked at the manual and thought that will be a problem.

i wanted to get the cylinder head remove and rebuilt by myself, can it be done with my skills: good manual understanding, good hands and proper tools (i am mechanical engineer)?

Yes. You are probably overqualified to do the job.

hey guys. i am also dong a top end rebuild. in my case, i melted a piston. it rendered the head and piston (obviously) unusable, and the cylinder was cracked. i purchased all OEM parts for my 98 WR400.

there is a link to that thread here.

i could use some advice on the '12 tooth / 13 tooth' timing issue between WR and YZ. specifically, does the WR timing make the alignment marks seem off compared to the YZ timing, or are they two different sets of cams completely?

thanks for checking it out,


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