74 400 Cross Engine Assembly Help?

Yeah, I blather on. I would reassemble with what you have and run it. You will feel the motors condition at kick and run. But I would keep looking for the next size piston and ring. There are a lot of running bikes out there that never start, smoke, rattle, die and never restart until cooled or wipe the ring. All chances we take with these old girls. New piston and ring with a bore will reduce the chance of any of these problems. I hope you mistyped the 1.5mm or I am not understanding the measurement. They are talking about the ring ridge at the top of the cylinder "B" and the cylinder wear "A" No more than "0.15MM"! The ring wears the cylinder and ring but the piston top land never wears the cylinder leaving a ridge at the top of the cylinder. Chris

Over the years these two are the only piston related measurements I've used. Frankly, I don't think piston skirt or ring gap would last long enough for the top of the piston measurement to become relevant.



If you're doing serious vintage racing every weekend then re-bore it, if its anything else then try what you have first.

I agree with Crash. Run it!!

Crash, I'm not doing vintage racing every week. I might like to but my wife has health issues that mean I can only get away occasionally.

There's no ridge at the top of the cylinder.

Yeah, I'm thinking of running it but I'd like to get a ring because manual says 28 thousandths end gap and mine is about 32.

I just read your profile!! 75!!God bless you! I hope I'm still at it at that age. Try Dave Pratt at Hva Specialty. He shows a ring for your 400.
https://www.hva-specialty.com/

Chris, Thanks! Well, in 6 weeks I'll be 76. I've been pretty lucky with being able to stay healthy & it's only in the last year and a half that I feel like I'm slowing down. I think most of the reason for that is because my wife has Parkinson's and it's getting to advanced stages. I'm pretty much active duty caregiver 24x7 now with only occasional relief from our 2 daughters and now and then a friend will stay with her so I can ride. Otherwise, I'd still be pretty active. Here's a picture from 3 years ago, I think, so I'd have been 73.

That's my 'Modern' bike. 2002 Honda CR250.


Cheers!
Bob

I would love to be healthy enough to be able to still ride aggressively and even compete. Nothin' like the adrenaline rush that comes with putting the power to the ground with a WOT.

Enjoy it while you can.

Crash, and I would love to see some current pictures of you racing, and even crashing! Hope you can get back to be able to do that.

I don't have any pictures from this century. And who doesn't love a good crash picture or video! Its one of the reasons I follow Pro Motocross. Those guys are at a skill level most of us can only dream of and when they exceed the envelop its pretty gnarly. MXGP is also amazing.

Heres a link to pictures of Huskys desert racing in the 70's that you may find entertaining.

http://www.cafehusky.com/threads/vintage-husqvarna-desert-racers.29894/

OK, been a while since I've posted. I stalled on the Husky over the piston issue. Decided to go ahead and bore it out to 1st over but then could not find a piston. Vintco is out of stock and said it would be 6 weeks to 6 months so I put it on hold and have been trying to get my Yamaha street bike running after 17 years.

After running into roadblocks on that project I've come back to the Husky. Have just about decided to go ahead and get a standard size piston that I found on ebay. It will leave me with about 5 thousandths clearance but the Husky manual says the service limit is .2mm, which is 8 thousandths so it should work.

Anyway, i'm looking at the clutch and have a question. These clutches with aluminum plates get very deformed & the fiber plates were really bad so I ordered new ones from Barnett. If I'm reading the parts manual correctly it looks like the other plates are 2 steel and 4 aluminum. I seem to have a number of steel plates so I'm wondering if it would work to replace the aluminum plates with steel. For one thing, I'd have to order new aluminum plates while I already have the steel but the steel would just be more durable. Thoughts?

Based on the shop manual max piston clearance is actually .012" but the piston rattle above .008" is more than I can stand. If you install the used piston then .005" is acceptable.

Thats a good question. It's my understanding that aluminum expands more than steel so clearance shouldn't be a problem with all steel. Weight isn't an issue. Wear on the fiber discs may increase by using all steel. I guess what I'm saying is I don't know . Try 'em and see.

Keep in mind that the pressure plate only moves about 2mm when de-clutched. That equates to a minute .2mm clearance between each of the 6 metal plates and 5 fiber-disc when de-clutched. Its my experience that new Barnett fiber-discs don't allow the bike to roll easily when in first gear and/or go in and out of first gear at an idle, probably due to the larger surface area than OEM discs. You may find that a low viscosity gear oil is required to provide proper de-clutching.

Something else that comes to mind when fitting new Barnett fiber-discs to the large clutch is to make sure they're able to move freely in the clutch basket slots. I had a set of Barnetts where the dogs, located on the perimeter of the discs, were too tight prevented them from floating free of one another while de-clutched. If your new discs don't easily slide into your clutch basket you may have to file a couple thousands off one side of each dog.

Crash, I'm referring to the manual I found online Husqvarna All 2-Stroke Repair.pdf. It shows .2mm. The Clymer manual does show .012 (actually, it shows .12 but that's obviously a misprint) but I never trusted that. Seems way too big. The problem with just bolting it together is that my ring gap is something like 30 thousandths. I found a ring on ebay for $50 but there's a standard size NOS piston for $70, with ring, and I'm leaning towards buying that. I expect it will be a couple thousandths larger than my used piston due to wear so it should work OK.

Yeah, the Barnett plates do seem pretty tight in the gaps so it's probably a good idea to take a little bit off of them. Plate thickness could be an issue. Manual says the whole shooting match should be a minimum of 28mm but says nothing about maximum size. Clymer manual does not deem it worth mentioning at all.

Over the years I've had occasion to fiddle some with Bultaco clutch plates, which are also metal. If I have to shave a couple of thousandths from a plate or 2 I should be able to figure it out. Just thought maybe the experts here might have some insight - and I was right! Thanks for your help!

And soak overnight in oil.

Dear Death, Pretty sure my wife won't like if I do that...

Or did you mean to soak the clutch plates???

Heres the repair manual page I was referring to, the bottom image.

Thought you may be able to use this bit of info regarding number of turns for pressure plate nuts. Didn't see it in the manual you're following. If your new Barnett plates drag then 7 turns may be better.

Yeah saturate the plates in the oil of your choice and what crash said.

I know. I was making a joke. Apparently, not a good one...