Messages

1

Tech Talk / Re: PVL Timing

« on: May 03, 2025, 06:15:21 pm »

For those interested, I've solved the leaking crank seal problem.

The seal I removed had some small notches on the inner lip, possibly caused from not lubricating the shaft before installation. I also had a good look at the shaft and casing, and they look in very good shape.

I followed up with a leak-down test with no leaks from the seal but a leak from the decompression valve thread (a drop from 5psi to 3psi over three minutes). I fitted a tight-fitting o ring over the valve thread and that solved the problem. I still had a leak but found it was coming from the air inlet fitting on the leak-down tester, so I've had a win. Onwards!

Thanks to those who helped out with advice.

2

Tech Talk / Re: PVL Timing

« on: April 18, 2025, 09:19:17 pm »

Thanks, pokey.

I'm guessing poor installation. I'll get a new seal next week and try again.

3

Tech Talk / Re: PVL Timing

« on: April 17, 2025, 03:11:06 pm »

Was very careful with the pressure, pokey. Took it slowly to 5 psi and it dropped fairly quickly. With a soapy water mix sprayed over the seal the leak was very evident around about 50% of the surface.

I now see that assembly lube or grease should have gone on the crank surface before the seal was fitted and I didn't do that. It went on dry. Could that be the problem?

Re: seal fitting. That was on the clutch side. This side was a much firmer fit when I installed it. I also used a wipe of threebond.


Am about to remove the spring off the seal and see if I can inject some oil or assembly grease under the lip.
Update: Still leaking.

4

Tech Talk / Re: PVL Timing

« on: April 17, 2025, 01:36:38 pm »

I have just reassembled my motor and a leak down test has air coming out the stator side crank seal on the inside where it wraps around the crank shaft.

When I disassembled the motor, I inspected the area around the stator and there was no sign that oil/fuel had been leaking from the seal. Makes me think I've got something wrong during reassembly. The seal is new and genuine Yamaha.

Can anyone suggest what's gone wrong?

5

Tech Talk / Re: Wiseco Ring End Gap

« on: April 10, 2025, 06:20:59 pm »

As Wasp mentioned, 'minimum' looks like the key word, which I overlooked when reading the destructions.

The workshop manual lists standard gap as .35 - .50mm, with .8mm as the limit and, although Wiseco may have different specs, it wouldn't have hurt me to read that a little earlier than just now.

6

Tech Talk / Re: Wiseco Ring End Gap

« on: April 10, 2025, 10:24:57 am »

I would say the gap should be MINIMUM  .35  . Yours is only .13 more than minimum =4 hairs..... I wouldn't worry, especially on a big piston that expands a lot. Better too much than not enough.

Thanks for your help.

7

Tech Talk / Re: Wiseco Ring End Gap

« on: April 07, 2025, 03:31:53 pm »

Multiple measurements around the bore are showing up 87.5mm.

The end gap reading is taken about an inch down the bore.

My verniers are pretty old but they've never given me reason to doubt.......until now.

8

Tech Talk / Re: Wiseco Ring End Gap

« on: April 07, 2025, 03:03:56 pm »

I would guess a few more bore measurements taken at various points? I've only ever used my 'eyecrometer' for a guestimate.:-)

I measured in two spots, one which looked like it would be the most worn.

Will do some more measuring and get back to you.

9

Tech Talk / Wiseco Ring End Gap

« on: April 07, 2025, 02:47:15 pm »

Wiseco recommended ring end gap for my WR500/YZ490 is .35mm (.0137 inch).

I am about to install new rings and the gap is .485mm (.019 inch).

The bore is 1st oversize (87.5mm), as are the new rings, and a measurement of the bore shows it bang on 87.5mm.

Can anyone suggest why the gap would be so big and also if this ring gap is acceptable?

10

Wanted / Wanted: Bearing Cover Plate

« on: March 20, 2025, 03:17:49 pm »

For Yamahas:

YZ 250 - '85, '88-'94
WR250 - '89-'93
YZ490 - '85-'90
WR500 - '92-'93

Part # 3SP-15381-00-00

11

General Discussion / Re: New Members

« on: March 19, 2025, 04:59:17 pm »

I happen to notice the latest new member Kurtas. Out of curiosity I checked the date , he joined in 2022 . That means no new members since 2022. What is going on ?

Covid must have killed the old timers ;-)

Don't worry John, I get the humour in your comment.


Interestingly, forum stats for 2024 and so far in 2025, show Most Online and Page Views are way up on previous years.

https://forum.ozvmx.com/index.php?action=stats

Plenty of people using the forum, just not contributing.

12

Tech Talk / Re: PVL Timing

« on: March 14, 2025, 03:29:34 pm »

Thanks folks.

13

Tech Talk / Re: PVL Timing

« on: March 13, 2025, 08:15:08 pm »

What's the best way to apply threebond to the crankcase without putting too much or too little on?

14

Tech Talk / Re: PVL Timing

« on: March 05, 2025, 08:37:07 pm »

I like your simple approach, John. I procrastinate way too much.

15

Tech Talk / Re: PVL Timing

« on: March 05, 2025, 07:32:18 pm »

Hi Tomas,

Watching a youtube video of an older yz490 motor assembly (mine is the same as the later '87-'90 motor), it seems a crank installer tool can't be used for the clutch side. The guy just applied a small amount of heat to the bearing and the crank slipped in very easily.

I haven't installed the stator side seal yet and expect if I do it after joining the crankcases I'll need a pipe or tube to fit over the shaft to push the seal into place. The guy in the video used a crank installation tool to push the crankcases together with the seal already in place.
It seemed to work well.

As you mentioned about using case bolts to pull cases together, yes, that doesn't seem ideal. I think I'll be able to borrow an installation tool to do that job.

Thanks for your advice.