wr 430 piston crossover

anyon know if the husqvarna cr500 piston, yamaha wr500 pistons are compatable with the wr430 air cooled cylinder of same bore size, just looking at more available options.

The Yamaha piston may be higher than the Husqvarna piston for the wrist pin to dome height. You need to check everything when cross referencing.

The husky 500 two cycle piston is around one pound, the 430 one is around 12 ounces with a smaller diameter wristpin. The earlier stock mahle husky pistons are a bit heavier because of more cut out (later ones)of the sides and the cut is higher (with piston upside down) at the transfer. The later mahle 430 has really too much shortening to the wristpin compared to the earlier 420/430. The ring is a bit higher, closer to the crown on the later mahle ones. I blieve both wiseco and Woosner (perhaps branded other things in other parts of the world) offer 430 pistons, crown to wristpin of correct dimention. They are a closer match to the later stock pistons than the earlier. If you go to my profile page and then to a website one can add to their profile pretty much every picture I have used on here is there with naming so figuring out what it is should be easy. The piston with the cardboard near it was a replacement offered during the cagiva, moto morini, etc era and the transfer notches align correctly for the air cooled 430.

The only two cycle 500 I know of with a longer stroke than the husky 500 is the kx500 so I suspect the others if applicable would have to be over bored. Maybe look at pistons in the 450cc range brand x.

the evolution of big bore Husky
400 bored to 430
430 stroked to 500
the wrist pin height is radically different on the two
as stated above you could look at other brands,,,,,,, but why not look at the aftermarket
or a good used Mahle
they are tougher than you think, unless something catastrophic happened you should need a bore and piston
i have 2 pistons on the shelf OEM Mahle but when i looked at the Wossner i saw no real issues with using one of those at some point

wasnt the 400 a de-bored 430? pretty sure the 400 was never around in air cooled form. the mahle are a pretty good piston. i have to say i like wossner better but i would have zero problems using a mahle. tried and true

We are getting a bit off track here. There were 400 and 450 before the engine cases post 1 is about.
One guy I know rode the 400 to high school, another had a 450 desert master. That stuff is really beyond my information base. I think after the air cooled 430 they had a water cooled 400 then made it 86mm bore 430.

The main problem with Mahle is they crurently produce stuff for the parent company that sold off the motorcycle division.

Wossner pistons for the 430s are readily available and relatively inexpensive,

http://www.ebay.com/itm/Husqvarna-C...Parts_Accessories&hash=item23451d616c&vxp=mtr

these are always on ebay . / everywhere . among others

thanks nz have already ordered one, i was doing a search and found some 2 stroke pistons of the size required but was unable to get the rest of the info required to confirm a valid crossover, just wondered if anyone had used an alternative with success.probably would require detailed specs on pistons pin location height skirt length etc. found some sites list the part as in stock but upon contacting have zero.

whats wrong with a wossner?

I will attempt to answer that but let's say what I put is less than ideal. I only have one 430 piston I bought from woosnerusa so don't forget to factor in.
a) compared with what came out of my 1998 wr125 it is pretty crude, not sure how it compares to what is in your 90's 360.

b) it is forged not cast hence expantion due to temperature change properties generally associated with that.

c) the notches at the transfer are not an exact match with the origional or the cylinder. If they stick in I suppose they could be trimmed if they are larger (I seem to remember that is the two ring one not the woosner one) it may not be an issue. The cagiva replacement had stiffening which would be eliminated to make them fit the water cooled cylinder or perhaps for porting.

d) Just guessing here the ring is like the water cooled mahle, closer to the top, I suspect this was allowed by going to water cooling so less than ideal for air cooled applications run hard, packed with mud, hot ambient temp etc. Pretty sure the later mahle has a spot for the clips so the longer one can be used.

I may add more the following are general comments






Note how the pin is offset in the second and third picture. That is different from origional.

One of the o's has two little dots over it which I could figure out how produce here If I wanted to bad enough.

Contrary to that ebay listing the woosner one weighs the same as the later Mahle.

Usually oversize pistons get heavier because the inside isn't expanded. At least the Husky and Norton stuff I have dealt with.

The wristpin length is longer than the later Mahle but less than the earlier Mahle. Quite possibly will hammer loose in the piston if revs go high. Doesn't seem to have that issue in auto applications from what I have disassembled. Look at the third picture down for evidence.

this is early,late,cagiva,/?wiseco?

Mahle pistons are probably the best in the world. They are 'seasoned', so the bore can be tighter without fear of seizing. The only drawback is the price, and hard to find certain pistons, but the Mahle's usually outlast any other 3 to 1 under the same punishment, so I would say they are cheaper in the long run.
I did a few experiments with Wiseco's, and Wossner's are very similar, where I measured the piston at room temp, then heated the piston in an oven at 200 degrees for about 10 minutes, then re-measured expansion. It had expanded over 6 thousanths at the skirt. If you were the use Wiseco's recommendation for clearance, and just raced the bike, it would have had some seizure's for sure.
This is the reason for proper break in, and Husqvarna's recommendation to thoroughly warm the motor up before even putting the bike in gear.

I ran into problems in the past in the drag racing engines with a problem between clearances with the cast pistons and forged pistols. The cylinder to piston with cast pistols was .002" and for forged pistols it was .005". For car engines. This tells me that forged pistols expand more and need more clearance. Is there a tighter clearance for using cast positions in the a.c. husky?

I experimented with a street engine I built to drag race specs to see how long it would last. I put the cylinder to forged piston clearance at .009". I installed all the goodies corvette 300hp cam, big block oil pump 90psi oil pressure, roller timing chain etc. The chevy 350 ran awesome for 100k miles. I pushed it too. I did runs to vt in 2 hrs 30 minutes. Normally 3.5 hours. It started burning oil at 100k she needed rings.

Paul,
Could you explain what a seasoned piston is?
Was that 200F or 200C?
Thanks

Doesn't the big bore evolution start with the 360=390=400=420=430=500 piston wise?

aluminium expands with heat greater than steel so i would imagine a forged piston in a steel liner would need greater clearance esp if aircooled due to higher running temps, i did find a wr500 piston that was 87.46mm as opposed to 87.42 on the husky both air cooled with 87.5mm bore, my machine guy wont hone a cylinder unless he has the piston as well he claims that without measuring the piston you cannot guarantee a good fit.regards small end bearings is wider better?.

The 360 and 390 are an earlier engine class, my 360 actually has rubber dampening in the clutch basket I might get a Husqvarna 390 chainsaw some day to fill that number.

As to the others right at the switch over dual shock to mono shock a water cooled dual shock 400 came out, again not the first 400 since you like to mix engine classes.

420=430 piston wise

As to 420,430,500 they all came to this market for the first time pretty close the 500 in my opinion being the most advanced with a different reed block and "Quad port" transfers as they are called elsewhere. 420 being it's own engine class, auto. Remove the 400 from your chain transpose 430 and 500 and you have the auto evolution as imported here.

The 360 has a divided exhaust port, I believe 360 was both piston port and reed valve some pistons have one hole and some have two, free answer take at that value.

I noticed the piston wise a bit late. the 400,420,430 really don't evolve the way I look at things. The way the blank is carved and the size of the blank may vary. 500 also I see two ways it is carved.

I have three new husqvarna chainsaws. The 385xp is a powerful saw. We put a 32" bar with the skip tooth chain and she chewed through 50"+++ diameter wood. The 575xp is also a saw that can hold its own. But it took cutting 20 cords of firewood to break them in. Now there even better. I have the 353 for liming. My next saw when I clear my land up north will be the 395xp. With three of us cutting.

I really like the hit and pull of the 390cr.

The 385 is the predecessor to the 390. Series 3 88cc. From what I have seen on line the insides of the cylinder with the exception of the intake is extremely like the liquid cooled 430. Possibly Mahle cylilnder and piston some of them are. I have been having some quality time making/restoring trail with a 338xpt.

Compared to stuff in modern bikes I don't see a lot (any?) of evolution in piston construction across 81 to 88 would have to inspect a 360 piston as I don't recall.

I never had a problem with my husqvarna 2100(99cc) chainsaws with the SEM ignition.
My first 83 250wr sem went south after one ride.

I use only the 2t husqvarna oil in there saws. The tolerances are tight so break in time is needed. Do not use any other oil than the husky oils in there saws.