high compression piston.

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S

sparks

Joined
Sep 8, 2006
Messages
989
Location
Hayle Cornwall
It's been said that the 450 piston will give you an upped compression on the 550 and 650 how do I know what I have, the piston crown in mine is perfectly flat, is the 450 slightly raised.
I was looking at the workshop manual nothing in particular and just happened to see on the page where they fit the piston the piston crown is concaved hence my question.

Regards

Sparks.
 
it's said that the 470 piston gives higher comp steve?

as swedish steel said recently though: the newer pistons are far lighter than the old stuff and this is more important.

first task should be to get the squish right. try to get .035" to .040"

regards

taffy
 
It depends on the year sparks.

In 04 the 650 piston went concave, previously it was flat (I don't know about the current 628 variety). Up until then the high comp mod was to use the 470 piston which had a wicked ramp (angular rather than smooth) or a couple of other aftermarket makers.

As fourstrokeforce says, in 07 the 450 has a dome.

It gets confusing and difficult to follow.....

All the best,
Simon
 
Simon said:
It depends on the year sparks.

In 04 the 650 piston went concave, previously it was flat (I don't know about the current 628 variety). Up until then the high comp mod was to use the 470 piston which had a wicked ramp (angular rather than smooth) or a couple of other aftermarket makers.

As fourstrokeforce says, in 07 the 450 has a dome.

It gets confusing and difficult to follow.....

All the best,
Simon
Click to expand...

Thanks for that mine is a 550 04 which had just had a new piston and crank when I got it, but with seeing the photo in the manual that showed a dished crown I was wondering if mine should be the same and the flat top piston which is now fitted has made it higher compression.

Regards

Sparks.
 
first task should be to get the squish right. try to get .035" to .040"


taffy,
i understand now how enginehardware got his squish right(with the 670cc stroker crank)
being 3mm longer(1.5mm futher down+1.5mm futher up).

now, how do get the squish right using a std crank and rod.
like we have been saying hi comp pistons reduce the squish but bad cause they weigh so much.gain performance one way lose in another.
..weed..
 
As the cam chain tension is VERY sensitive to any adjustments on deck height, gasket thickness or cylinder head height, things are pointing in the direction of having your own special piston produced. I, for myself, had to go there because of my large valves and valve lift. To get low weight, and strong design, it is crucial to find a manufacturer with a good 100mm forging. The Wössner pistons are still too heavy in my opinion. Still looking.. Any tips would be appreciated! I have designed a complete piston in 3D CAD, but I shouldn´t have to make my own pistons as well, do I?
 
popup said:
first task should be to get the squish right. try to get .035" to .040"


taffy,
i understand now how enginehardware got his squish right(with the 670cc stroker crank)
being 3mm longer(1.5mm futher down+1.5mm futher up).

now, how do get the squish right using a std crank and rod.
like we have been saying hi comp pistons reduce the squish but bad cause they weigh so much.gain performance one way lose in another.
..weed..
Click to expand...

i have no doubt IMHO. you must either increase the length of the rod to 136-137mm or as i used to do - lop the correct amount off the top of the cases and spigot although as you know, i have a slightly 'proud' spigot for better cylinder sealing.

there is a thin gasket available in the doc to help but i would save that for after machining work so you could bring the piston to had nearer if it's available.

one piston or another won't vary even a thou from the same manufacturer but the different makers may well be all over the show!

by machining the barrel you aren't changing the balance or adding any weight.

your next problem is the camchain. the camgear teeth won't line up! they will be 2mm out as measured at the outer circumference of the gear.

you can slot the gear for this. there is more than enough meat for this. careful study of the doc will also show that moving of gear teeth in the primary drive one way whilst 'reversing' this with the cam gear will bring you close.

BTW, if anyone has a 100mm piston (new) about i need one.

regards

Taffy
 
i don't know what the piston squish is on the 450/550 but like i said on my old 650 , the piston comes up 2mm below deck height + the 1.4mm head gasket =3.4mm squish.with these specs
the book says my compression ratio is 12.2:1
for instance if i adjusted my squish to .040" or 1mm (2.4mm off what i got now) i recon i would have to be at great risk of detonation, would't i ?
the way i see i is ,the only way you could run a 1mm squish, is with a cam with heaps of overlap like a x1 or a crate engine cam.tell me if i'm wromg?

dr c , enginehardware was telling us that elko pistons are the lightest.

taffy,i see how you readjust cam timing,but you only have to skim 1/2 a fly poo off deck height and your cam chain will have no adjustment.
whatever you take off deck height ,you have to fill on the bottom of the cam bearings,then machine out the same amount in the rocker cover.
..weed..
 
i don't think it's as bad as you say popup? if you are bringing camchain adjustment into this i suggest you try a little experomenting.

remember that the very early 400s (and maybe others?) had a 1" alloy knob on the end. then they went to a shorter one and then they got rid of them completely.

i believe i still have a photo of my early tensioner in my gallery and the doc. the alloy knowb was very long.

regards

Taffy
 
popup said:
1. for instance if i adjusted my squish to .040" or 1mm (2.4mm off what i got now) i recon i would have to be at great risk of detonation, would't i ?

2. dr c , enginehardware was telling us that elko pistons are the lightest.
Click to expand...
1. Improper design of the combustion chamber (given the fuel is burning at "normal" speeds) is causing detonation much more likely than just tiny squish. Sharp edges at the piston top can fx cause very lokal detonation problems. Don´t worry Weeds, the squish areas in a Husaberg are not that wide/deep that it will get you in trouble. -Tune away! :D

2. Yes, the Elko piston is very light and gives an almost good squish. It is however not lasting very long, or providing a decent geometric compression ratio.
 
as said, wrong about the chain.

to check the real compression you need to remove the head, get the piston to TDC, smear vaso into the gap twixt piston and linar. headgasket, head on, lightly torque, place engine slightly over so plug hole is highest point, use a syringe to squirt in paraffin or similar. stop as the paraffin enters the plug thread.

if say 64cc you have to add that to the engine size which is either 644 or 628. 644 + 64 =708 and then divide by 64 so you get 11.06 to 1 compression.

to get the area you would gain which i take to be 2.4mm of the swept volume it is:
pie r squared x radius x radius x 2.4
3.142 x 50 x 50 x 2.4= 18.85cc

so you know that 64cc would become 45cc of paraffin etc etc.

so 644 + 45 = 689 divided by 45 for 15.31 to 1 compression.

but as Dr C would tell you, you would machine around the inlets and then do a bit to have secondary squish and then we have to machine big recesses in the piston coz you are now 2.4mm nearer. so you'd be amazed how hard it is to get a really high compression.

i hope you found this useful.

trust you have the 35mm big end?

regards

Taffy
 
all good info lads,even if i will never use it.maybe someone else will.
when a 450 beats my old girl in drag race then maybe....can't see that happening
..weed..
 
is that all you can say? a shekel for me life story?

how about a penny for an ex-leper?

regards

Taffy
 
Hey Guys,

Did we ever come up with a high quality, light and durable high compression piston option for the 04-08 650?

Thanks!
 
How high do you need ?

For standard Comp 05-08 can use Wossner 570 piston in backwards

The compression ratio and squish spec are the same as oem elko but the shape of the 570 piston is not ideal imho.

Use oem (price is ok) Or for higher Comp get the Ktm 540/560 Wossner piston and machine the top down to what you need.

Pro x is cheap **** I got 100 hours out of one.
 
Big Berg said:
Hey Guys,

Did we ever come up with a high quality, light and durable high compression piston option for the 04-08 650?

Thanks!
Click to expand...

well I sell one! i call it the 'tall boy'. OEM is really good quality.

regards

Taffy
 

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