Cam timing question

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BSirBike
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Cam timing question

Post by BSirBike » Tue Jul 07, 2020 9:47 am

Hello again folks

While I've been waiting for some bits to arrive (Royal Mail has been terrible :roll: ), I thought I'd do a compression test just to see how it is.

Shock...horror ! Compression results were around 39-41 on each cylinder :oops:

Dropped a bit of oil into the chambers where carbs sit (carbs are off the bike anyway) and also into spark holes and tried again. Compression now about 65-70 on each cylinder. Still way below 135 that I got written down from info I found somewhere.

I'm not very knowledgeable with these, but fortunately, a friend who owns a FZ750 and has dabbled with bikes for many years suggested taking cam cover off and check shims.

Next weird problem was that quite a lot of oil flowed out of the top as the cam cover was being loosened, almost 1/2 litre. Is that normal ?

And finally, I removed the cover on right side of engine, so I could turn the engine by hand clockwise, and after a couple of rotations, managed to get the holes in the cam to appear together. But looking at the photo below, I think the cam timing is off ? No idea how to check/sort this out. Any ideas please ?


https://ibb.co/C5HxLR9

BSirBike
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Re: Cam timing question

Post by BSirBike » Wed Jul 08, 2020 8:52 am

Bit of an update on this.

Did valve clearance check, and there are a few that are just at the 0.11mm to 0.20mm lower limit, and a couple below that, on the Intake side. Exhaust side are all within the 0.21mm to .30mm tolerances.

So will be taking out intake cam and checking the shims with the help of my friend.

One bit of good news is that we re-did the compression test using a different tool that my friend has used for many, many years, as we noticed my compression tool was not pushing in all the way into the spark plug holes, probably due to the design, where there is this little step on the area where the plugs go in.

So new figures are 135, 130, 132, 122. So cylinder 4 is a little low, but within the tolerances, thankfully.

Anyone know where to get hold of the shims ?

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Re: Cam timing question

Post by CMSMJ1 » Wed Jul 08, 2020 11:25 am

Shims are a generic part usually - they come in 2 diameters and can be bought new from the local moto shop I am sure
IMPERATOR REX ANGLORUM

The V4 is the law..

NC30 - No9 > Back on track
NC30 - In lots of pieces..still

BSirBike
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Re: Cam timing question

Post by BSirBike » Fri Jul 10, 2020 6:31 pm

Thanks for the heads-up. Got the intake shims out, and found Yambits do the correct ones, so ordered a full set, as tolerances are quite low.

Now, on the exhast side, the tolerances were good, except on cyliunder 4. So when I took out the exhaust cam, I noticed the bucket (under which the shim sits) was a bit battered, visible in the picture below

Image

So I took the cam and inspected it, and noticed that the corresponding cam lobe is shorter (about 2mm height) compared to the one next to it (picure below)

Image

Surely this isn't normal ? Either it's worn badly, or someone has machined it or something ? :whistle:

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Re: Cam timing question

Post by Evilchicken0 » Sun Jul 12, 2020 10:09 am

That cam is ... suboptimal by some way. I'd replace that !!!
I'd look on ebay for a secondhand one, get in contact with the seller and ask the model, dont rely on "1WG" because there are 5 models of them.

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Re: Cam timing question

Post by Evilchicken0 » Sun Jul 12, 2020 10:11 am

That cam might explain why you have a different main jet in one carb ... when you put this right remember to use a standard size jet.

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Re: Cam timing question

Post by BSirBike » Sun Jul 12, 2020 12:47 pm

Yeah, thought as much that the cam was gone. Found a page in the service manual with some measurements for the cam, and this one is mostly below spec.

I've found a set of cams on eBay, very clean, and bought them. The seller has no idea what model of bike they came off, so I am hoping they are identical to mine, otherwise I'll have to keep looking.

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Re: Cam timing question

Post by BSirBike » Sun Jul 12, 2020 12:55 pm

I've taken a look at the parts catalog for the valve lifter/bucket, as that one looks in bad shape, so I might have to bite the bullet and get a new one.

There are 2 part numbers shown for my 1WG model - 1WG-12153-20 and 1WG-12153-09. The 2nd one shows No longer available, but I found a couple of others with a slightly different part number (1WG-12153-30) for the 1989 US model ?.

Does anyone know what is the difference between these ?

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Re: Cam timing question

Post by Evilchicken0 » Sun Jul 12, 2020 7:37 pm

The US model is probably a 3bf ... they didnt have an exup and looked like the early Genesis.
I've got some spare thundercat ones if it helps ... and 3tj cams

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Re: Cam timing question

Post by BSirBike » Mon Jul 13, 2020 8:42 am

I emailed the seller to check what model the cams were from, and he said the cams he has are marked 3BF, and he believes they came off a 88-90 model bike. Not sure if they will be OK ? I was looking to swap out the intake and exhaust ones as the ones he has are quite good.

Do you have the cams from thundercat ? Or valve lifter/shims ?


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