• Husqvarna Motorcycles Made In Sweden - About 1988 and older

  • Hi everyone,

    As you all know, Coffee (Dean) passed away a couple of years ago. I am Dean's ex-wife's husband and happen to have spent my career in tech. Over the years, I occasionally helped Dean with various tech issues.

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    Thanks for your patience and support!

Matching piston skirt to transfer ports

ajcmbrown

ajcmbrown

Husqvarna
Pro Class
A question for the collective knowledge here.
While assembling my engine (88 250WR) I matched the cases to the transfer ports along with the base gasket, but when I slide the piston into the cylinder, there seems to be an excessive amount of piston protruding into the transfer port area.

Is there any benefit in trying to match the piston skirt to the transfer ports?
I am unable to completely match the skirt since it has two strengthening ribs on the inside of the piston that I don't want to compromise but it could be improved quite a bit.
Tony.

IMG20170313200140.jpg
 
That piston might match an earlier cylinder just right. I have a cagiva replacement 430 one sort of similar issue.
 
fran...k. said:
That piston might match an earlier cylinder just right. I have a cagiva replacement 430 one sort of similar issue.
Click to expand...


The original piston is very similar, I guess I'm looking to remove any inefficiencies or bottlenecks in the transfer port area.
 
On further consideration that 250 is a different bore stroke than the earlier ones. It connects the transfer area to the reed cage. It has been a long time since I looked at one of those. You might study what happened over time with the 250 Husky or Yamaha or other that did not go to a reed valve. I will let someone else that actually has dealt with that model to help further.
 
Take a look in the vintage tech ref and parts , page 3 , vintage race mods/tech tips . Look for poplar cycling 125 mods and see what how they modified the piston . Yeah I know it's for a 125 but found the same issues on my 81 430 . At bottom dead center the piston under the wrist pin would partially block the transfer ports . I did this mod to the 430 back in 81 , no I'll effects that I know of . Didn't do it this time only because of no access to a milling machine ... Yet . Hope this helps .
 
Maybe it is of little value performance wise due to the short time the piston is at BDC, but like you, I see no ill effects from doing this, maybe it'll help a little.
Every time I look at it, it just looks wrong.
Tony.
 
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