Temple for the tuners?

[mj43]

I stumbled across this site yesterday.
Some interesting stuff on there

http://www.pit-lane.biz/f34-gp125-et-250-snif

[Top-shaggy]

Thanks for the link MJ =D>

Wish my French was a little better for some of it.. But at least it gives this dinosaur some practice

[500bernie]

I scanned through looking for familiar phrases from my french lessons at school, such as:
Look at the Bertion family
See the wundow
And the most popular one......
Campbell you idiot......get out and report to the headmaster

[TwoStroke Institute]

I stumbled across this site yesterday.
Some interesting stuff on there

http://www.pit-lane.biz/f34-gp125-et-250-snif

Your only 2.5yrs late/behind.

[JanBros]

I scanned through looking for familiar phrases from my french lessons at school, such as:
Look at the Bertion family
See the wundow
And the most popular one......
Campbell you idiot......get out and report to the headmaster

if you need something translated, just post it here and I'll do an effort

[500bernie]

Thanks Jan
I can always rely on a helping hand being offered here =D>

[TwoStroke Institute]

Important bits are all in English

[mj43]

It is an interesting thread in particular the information supplied by Fritz Overmars and Jan Thiel (all in English)

An initial scan of the 85 odd pages indicates that most of the modifications I do to the crankcase are the right way to go. The changes I make to the barrel are also the way to go

Comparing with the RSA barrel it looks as if the KR barrel is a pretty good design.

[TwoStroke Institute]

It is an interesting thread in particular the information supplied by Fritz Overmars and Jan Thiel (all in English)

An initial scan of the 85 odd pages indicates that most of the modifications I do to the crankcase are the right way to go. The changes I make to the barrel are also the way to go

Comparing with the RSA barrel it looks as if the KR barrel is a pretty good design.

Mark surely your having a laugh? Have not seen where you have advocted, more not less case volume is the way to go, opening the sub exhaust ports after the main is the way to go, exhaust ducts that are smaller not bigger is the way to go, a mismatch at the cylinder/flange is the way to go, why knife edging transfer divider is a bad thing, the perils of a wasted spark ignition, thermal management within the engine and running a 115mm or 120mm rod is the way to go.

KHI got the KR-1 and the KR250 right with the inner wall of the transfer and a triple port is better than a bridged.

[mj43]

I am not sure what you are saying as part of the info you have supplied is contradictory and the way you have worded it are you attributing it to me or others?

On rod length Jan Thiel talks about Rod to bore ratio (part 2 page 34)

A 120mm rod is for a ~54.4 mm stroke not a 50.6 stroke. For rod length they use a factor of between 2.17 and 2.2 of the stroke. So for a KR between 109 and 111 mm would seem appropriate based on the information they have supplied. A 120mm rod is 2.37 ratio well beyond anything they mention - or are there any pearls you would like to share with us? They do not mention basing rod length on capacity....

Also interesting to see how the oil feed hole for the mains sits in a smooth transfer tunnel

KR Barrel was designed several years before the Aprilia and by all accounts is not a bad basic design - which you appear to agree with.

[mj43]

.... opening the sub exhaust ports after the main is the way to go......

The question has been asked but......

[maccas]

I think the sub port opening before or after the main debate comes down to the type of powervalve arrangement employed in the cylinder. Obviously there is the pressure pulse debate too, I won't go into that as it's beyond my understanding.

I have noticed that cylinders that have variable height main ports have the subs lower than the main port.

Cylinders with a fixed main port with subs have the subs higher than the main (in oem spec they do anyway).

TZ (3yl, 4dp, 4tw, early 5ke) have the sub port lower than the main. All of these bikes have guillotine style powervalves that only operate on the main port. The PV doesn't close off the sub ports at all. Hence the lower sub port. If the sub port was higher than the main port then bottom end power would be sacrificed due to not being able to close off the sub port.

With the KR the main exhaust port is kept relatively low to maintain bottom end drive. The subs are higher than the main to give extra time area and duration once the subs are opened. The sub ports can be high because they aren't open lower in the rev range.

Just my take on it anyway.

Dan

[TwoStroke Institute]

I think the sub port opening before or after the main debate comes down to the type of powervalve arrangement employed in the cylinder. Obviously there is the pressure pulse debate too, I won't go into that as it's beyond my understanding.

I have noticed that cylinders that have variable height main ports have the subs lower than the main port.

Cylinders with a fixed main port with subs have the subs higher than the main (in oem spec they do anyway).

TZ (3yl, 4dp, 4tw, early 5ke) have the sub port lower than the main. All of these bikes have guillotine style powervalves that only operate on the main port. The PV doesn't close off the sub ports at all. Hence the lower sub port. If the sub port was higher than the main port then bottom end power would be sacrificed due to not being able to close off the sub port.

With the KR the main exhaust port is kept relatively low to maintain bottom end drive. The subs are higher than the main to give extra time area and duration once the subs are opened. The sub ports can be high because they aren't open lower in the rev range.

Just my take on it anyway.

Dan

Nothing to do with the PV unfortunately Dan, and the answer is........................................................

[maccas]

Oh well we will agree to disagree then

Dan

[mj43]

In TSI's usual style unhelpful as ever. In the spirit of Frits Overmars an explaination would be useful. What Dan has posted seems perfectly reasonable.

Also have you decided whether 120mm rods are appropriate for a motor with a 50.6mm stroke?