• 2 Stroke Husqvarna Motorcycles Made In Italy - About 1989 to 2014
     WR = 2st Enduro & CR = 2st Cross

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250-500cc Wr 360 squish help

juicypips

juicypips

Husqvarna
Pro Class
Right im in need of guidance once again, unusual i know lol
Put 93 360 cylinder on the last month clocked 17 hours ride thought wheres my beast from before gone? So i measured me squish its at..... 2.73mm wow huge seeing as i thought it was supposed to be close to 1mm or 50 thou.
So i need to cut a whopping 1.7mm ignore the three for safety?
So my head before the band measures .83mm
And the deep groove in cylinder measures 2.09mm
I dont fancy reshaping combustion area so i plan to take .7mm from head
And a 1mm from top of cylinder re machine gasket rings, will this be acceptable?
P.s. My base gasket is .03 thinnest i could get.

Help me help me help me.
Cheers guys n gals
 
Your 360 is whole different animal. I would do some research before you cut that much off your head deck.
 
im not sure how you are measuring squish but that seems way off. what piston are you using? do you have a dial indicator to check it per shop manual? i had to use two thin base gaskets to get mine correct but its right on per book..i have a wossner in my 95. once i adjusted my pv it has a great spread of power, and pulls hard on the top end hit.
 
If you dont have dial gauge, you can also use solder squish band check to be sure.
 
No didnt check upon first assembly, just made sure there was no interferance as i was doing a rally on the weekend.
i used solder and am measuring the distance from piston corner to the corner of squish band, then im using digital calipers to read the solder.
2.6mm is huge tho.
Will have to get a dial indicator but couldnt see anything wrong with solder method.
Thanks for the pic is that for all years of 360 as the 93's wilder porting than the 2000's?
Its a wossner piston but the heads off a different bike.
I know if i go too small a clearance i risk holing my piston but ive got a lectron set up dam near perfect and am aiming for a bit more hit.
Basically shes not lofting the front like she used to an i miss it :,(
Still same gearing pv ive played with no avail
Carb made her run much nicer
Cylinder made top end wake up
Gnarly made more power
Boycesen reeds didnt notice difference... So i thought squish
 
wallybean said:
Your 360 is whole different animal. I would do some research before you cut that much off your head deck.
Click to expand...
Thats why i ask you... Reading the multi lingual manual is hard work.
Just being lazy and more opinions the better dont want to junk a perfectly good engine.

Oh i got the 1mm clearance as a guide from rd 350 settings i asumed most 350's would be around that area.
 
Dale Alexander also explains it well in his RD tuning articles in the ACTSO archives. Basically, any charge trapped in the squish area (between the piston and squish area of the head) does not burn, due to localised cooling from the heads material. So what you want to do is to keep that amount of unburned, thus unused (meaning it's just along for the ride and does not make any power) charge minimised. You get the gap (squish clearance) reduced to a safe amount so the piston does not whack into the head at max rpm. That gap is usually in the .030-.040" range. This squeezes all that once unburned(when the gap was.060") charge into the bowl proper where it gets burned with the rest of the mixture and helps create power.


This was one of the articles i got information from.
 
juicypips said:
Thats why i ask you... Reading the multi lingual manual is hard work.
Just being lazy and more opinions the better dont want to junk a perfectly good engine.

Oh i got the 1mm clearance as a guide from rd 350 settings i asumed most 350's would be around that area.
Click to expand...



that's not really appropriate as the RD350 was a twin so you have a 175 cylinder that also happens to be air cooled
 
juicypips said:
See thats why i asked! Lol whats your squish set at?
Click to expand...


funny but out of all the 360's i have never had a head off any of them
they run strong and long, this year i will pull my 93 down as it has the most hours on it and it is not running as sweet as it used to
but 10 years who's to complain ;)
 
juicypips said:
No didnt check upon first assembly, just made sure there was no interferance as i was doing a rally on the weekend.
i used solder and am measuring the distance from piston corner to the corner of squish band, then im using digital calipers to read the solder.
2.6mm is huge tho.
Will have to get a dial indicator but couldnt see anything wrong with solder method.
Thanks for the pic is that for all years of 360 as the 93's wilder porting than the 2000's?
Its a wossner piston but the heads off a different bike.
I know if i go too small a clearance i risk holing my piston but ive got a lectron set up dam near perfect and am aiming for a bit more hit.
Basically shes not lofting the front like she used to an i miss it :,(
Still same gearing pv ive played with no avail
Carb made her run much nicer
Cylinder made top end wake up
Gnarly made more power
Boycesen reeds didnt notice difference... So i thought squish
Click to expand...

not sure if the different porting on later years is going to change anything. the pic is from my 95 manual.
 
2,6mm is alot, but will have it reasons from factory i guess.
For the 2t race engines i have made and seen made snd learned from very experienced people is keep the squish tight for bottom end power. Especially if you make the exhaust higher as you will lose compression by doing this.
Best is to calculate the compression ratio to stay safe. Or just dont touch it :-)
 
juicypips said:
10years??? Not even a set of rings? Piston conrod? Find that very hard to believe do you actually ride it?
Click to expand...
my 88 250 is on the stock top end, i bought the bike as nos in 98. it has seen quite a bit of service, and still hits 212 psi on my gauge..im probably going to replace the piston just because of fatigue
 
Nuts pure nuts i think im getting good mileage from a years worth of hack about... Mind you im the type of bloke that out of 1000 perfect things i would pick the one thats problematic.. Lol
Im gunna tamper with the squish clearance set it to 55 thou whats the worst that can happen? I hole a piston grenade the bottom end and have £300-400 rebuild... Nothing ventured an all that.
I assume the tolerances are so huge due to vairants in rods pistons cylnders n head machining getting it exact and spot on in mass production is costly and time consuming.
Will give it a bash an keep you posted.

Thanks for your input guys n gals ;)
 
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