500 Two-Stroke Tech

I have another one or two with the CNC there's gonna be wild stuff...

Vinpg wrote:I have another one or two with the CNC there's gonna be wild stuff...

I can hardly wait to see what's next!

Not sure I understand why you went with 2 heads for 4 cylinders?

Seems like using 4 heads for 4 cylinders would be much lighter.

It's easier to plumb, uses stock everything

Read Dale Alexanders paper on " Squishing things till they make power " ( I think ) .
Most relevant to water - cooled & answers the smart questions recently posted .
Read it twice ...
The head / barrel alignment method is a little dated , but it does work .
If someone needs a less tedious procedure just ask .

jeff10 wrote:Read Dale Alexanders paper on " Squishing things till they make power " ( I think ) .
Most relevant to water - cooled & answers the smart questions recently posted .
Read it twice ...
The head / barrel alignment method is a little dated , but it does work .
If someone needs a less tedious procedure just ask .

I would love to know the best technique on aligning the heads Jeff, That would be great...

I'm going out on a limb and saying it's hard to center it, we have tried o-ringing stock head's like our billit ones and the castings are all over the place, cylinders are Dowel located and we have centered the heads to the bore

Ade SYM wrote:

David de Botton wrote:What other heads can be used as an individual cylinder head.
YZ125
TZR250 ?
Stud pattern looks the same

Cheers

I believe the TZR250 3XV SP ones will work but there is a little work to be done on the waterways. But good luck in finding a full set of 4 as i have been looking for a while!
Thanks Ade

I just purchased TZR250 3XV SP cylinder head....By the time I get it... it would have cost to much.
Would have been better using a 125 head from another model and modify it

The quick version .
Machine a plug that drops into
the bore ; it will need a lip / flange
that fits the recess of the step
left left by the head / squish
band machining .
The head can now be bolted
down and dowled .

Jeff 10 --- thank you...soon as I have 4 heads I intend to align all bores to heads then do the Squish clearances

Pop your head up when this
is about to happen ... I shall
run through this procedure
in more detail and importantly
the correct order machining
wise .

Jeff 10 - very kind of you,,,much appreciated

No doubt it will take some time to organise all 4 heads

Cheers

I have only used the 3ma SP heads...although some of the early YZ125 heads fit as well. There is a bit of welding on the outside of the head to match the cyl and some of the coolant passage need a little grinding (it was 6 years ago I built that engine so memory is a bit vague)...I did some extensive mods to the cases and the bottom of the cyls so the coolant could flow through the bottom of the cyls. into the crankcase (like on a YZR) and exit in the V via a large welded on boss. The hose then joined to a custom aluminium coolant tube that runs between the 2 bottom cyls....

Cheers
Mick

Where is the exit point from
the engine exactly ?
( sadly I have a spare engine ...
The coolant route I get ; the
exit strategy has me intrigued ) .

On the first page of this post, in the 2nd picture of the engine you can see the aluminium coolant pipe that runs between the 2 bottom cyls....half way along it you can see a black coolant hose running from the coolant pipe directly backwards towards the base of the top cyls......there is an aluminium outlet welded on to the upper crankcase just below the base of the cyls....water exits through there

Scarily similar to mine .
When I work out how to
post piccies I shall ..