Plastic Tubes on Case Studs

[Prothec]

I'm rebuilding a '78 engine and have pulled the cylinders to swap with another set. Should I worry about replacing the plastic tubes that go over the studs? All of them disintegrated when I pulled the cylinders. I would imagine they are needed to isolate the dissimilar metals?

If I should replace them, anyone know if/where they can be found or improvised?

[natemoen]

Don't worry about the bolt covers. Clean all the crap of the studs and out of the holes and reassembled.

[Prothec]

Sounds good. I'm degreasing it now. This is my slow and careful bike. I've been chipping away slowly at all the work to do on it for a few months now.

I plan to get it running on the carbs, then look into EFI!

[James England]

How easy did you find it to remove the cylinders?

[fredintoon]

I'm rebuilding a '78 engine and have pulled the cylinders to swap with another set. Should I worry about replacing the plastic tubes that go over the studs? All of them disintegrated when I pulled the cylinders. I would imagine they are needed to isolate the dissimilar metals?

If I should replace them, anyone know if/where they can be found or improvised?

Hi Prothec,
there ain't no plastic tubes.
What you got there is 3 decades-worth of accumulated crud.
From what others have posted, be happy that it disintegrated instead of locking the cylinders to the crankcase.

[natemoen]

Hi Prothec,
there ain't no plastic tubes.
What you got there is 3 decades-worth of accumulated crud.
From what others have posted, be happy that it disintegrated instead of locking the cylinders to the crankcase.

Actually Fred yes there where dampeners put around the studs from the factory.

[Prothec]

How easy did you find it to remove the cylinders?

It was pretty rough to remove. It took a few days. First to break them free from the gasket, then to soak the length of the studs in a LOT of PB Blaster, scrape and scrape, working the cylinders up and down.. A little careful pounding with a rubber mallet and eventually they popped off. I did break at least 1 fin, but the bike came with some already broken, which is really the main reason I was replacing the cylinders. The new cylinders only have one broken fin that the seller seemed to purposely hide in their ebay photos. It'll be much easier to repair though!


James, there were definitely some of the plastic tubes in place. A couple were cracked lengthwise, others broken up real bad. That must be the reason for them.. To help prevent the crud from seizing the cylinders to the studs?
Edit: who cares what they're actually for, apparently just Yamaha over-engineering!

There were a few on the studs on my XJ, not all of the studs though.

[James England]

On a scrap engine I had, I tried to remove the barrels, just to see how hard it was. They were ruined anyway with broken fins. I used a crowbar to no avail and I ended up hitting the barrels with a huge sledgehammer! And.... they still would not come off! Completely, totally impossible. It made me realise that I would never undertake removal of the barrels on my bike (not a single fin broken) lightly.......

[natemoen]

When I pulled the jugs off mine (the first time) they were certainly difficult but not impossible and I didnt break any fins. It is like anything else, take it slow and use appropriately sized tools. If you are using crowbars and big hammers then yeah you are going to break fins.

[James England]

It is like anything else, take it slow and use appropriately sized tools. If you are using crowbars and big hammers then yeah you are going to break fins.

I'd already done that, although only for about 2 hours. I even tried dental floss. Like I say, it was a scrap engine with badly broken fins and the purpose of the exercise was to see just how difficult it would be (in a time frame of a few hours admittedly). After trying everything else, except time over a couple of days etc, I thought I'd see what immense brute force would accomplish. The sledge hammer (8lbs) and crowbar were really to see if the jugs would stand that. They did.

Having said that, the above process was a good learning experience... The jugs are on tight. Fins break very, very easily. It made me realise how much care would be required to do it on my own bike. That, and reading comments here, means I would take time, lots of freeing oil (I like PlusGas), gentle persuasion.

Didn't someone post here that they'd made some sort of gadget to exert force on the jugs without breaking fins?

[natemoen]

Yeah, trbig post some contraption to pull the jugs.

[BA80]

Removing stuck cylinders

[James England]

That's it. Thanks. I'll file that one away for future reference....

[Prothec]

I must have way more patience than I thought

It definitely took time, paid attention to the prying points shown in the manual and lots of penetrating oil.