StinkWheels Two-Stroke Dyno Day 2008 - 26th July

kwackman12 · Post by **kwackman12** » Fri Jul 04, 2008 10:53 pm

Where abouts is it being held, cant see an address?

Cliff · Post by **Cliff** » Sat Jul 05, 2008 5:30 am

kwackman12 wrote:Where abouts is it being held, cant see an address?

http://gibsonexhausts.co.uk/stinkwheels/home/index.asp

mj43 · Post by **mj43** » Sat Jul 05, 2008 1:15 pm

mr_bungholeo wrote:last year on a stock(well worn)engine i got 54.7 on the dynojet 200..
with crank case work and a bit of fettling this year i HOPE to beat 60bhp..but on a dynapro...ide be lucky to show 50......bring a bike down mj.....i would love to know wot your race bike puts out with all the work....70+bhp?

Would love to but we are at Cadwell that weekend

We did 71hp once on a dynojet but that was an exceptional day (conditions) that engine usually made 65 ~ 66 on a dynojet about 60hp on a dynopro. The current engine has shown a couple more horse (62+ hp) but a much wider spread so I reckon it might make a repeatable 68 on the dynojet.

Next incarnation - have the barrels sat on my desk should be a few up on that and I am hoping next years Bonneville engine will be a couple up on that again (8 to 10 more than last years Bonny engine). I know they are big claims but I reckon I can do it just got to get my finger out. A reliable, repeatable 70 to 72 dynojet hp, 64 to 66 DynoPro is my target. Should easily top 140mph target is 145 but I think that is a tall order. Real goal a dream but got to be able to dream, is to beat the 500 record held by Yammagamma on the RGV forum on an RG500 at 148mph.

the-elf · Post by **the-elf** » Sat Jul 05, 2008 1:45 pm

My current engine is about 4 bhp down on MJ's, but there is still a couple more to come from that set of barrels, I plan on swapping these for my new set next week once I get them back from plating and then finishing off the the current set and then either sell them or keep them for spares as they would be excellent on a road or a wet bike. I tried something different with these and lost some top end but got a broader smoother spread of power.

I have now changed the porting on the new one's in accordance with what I have learned and what I managed to weadle out of MJ

which confirmed what I was thinking. I know my new set should be up there,

trouble is MJ seems to be always a step ahead

.

I might have to consider going over to a single ring piston, with a rear facing pin as that would allow me a bit more freedom in tuning .

mgtkr1 · Post by **mgtkr1** » Sat Jul 05, 2008 1:54 pm

might be up for this dyno day? will see what i have planned, if anything. with new rings i ''should'' see about 62hp. at the height of this motors time, stans kr's made about 66hp witha strong drive for ''selected'' people. the cases are flowed nicely but imo not worth the 80.00 that it cost back in the early 90's. the way i have done mine on another motor as shown by mark is much better. not sure what the diffrence would mean on a dyno but i suspect the more efficent and the smoother the flow path (mine and mj's) the smoother the power delivery. who else is going? and what engine work have others had done? elf, your right in thinking the tz piston allows more scope for bigger ports. we'll see what happens at the dyno (really need to book a proper session more local) and if your happpy i will send you a port map, specs etc and a copy of the printout so you can copy a set of your spare barrels. what hp did you get last time kev? i know you had some issues but still irc you had good power.

JanBros · Post by **JanBros** » Sat Jul 05, 2008 6:52 pm

the-elf wrote:I might have to consider going over to a single ring piston, with a rear facing pin as that would allow me a bit more freedom in tuning .

what then with the rear facing transfer port

the-elf · Post by **the-elf** » Sun Jul 06, 2008 9:28 am

JanBros wrote:
the-elf wrote:I might have to consider going over to a single ring piston, with a rear facing pin as that would allow me a bit more freedom in tuning .
what then with the rear facing transfer port

As the port dosn't have a shape edge they seem to be quite happy. MJ and Mat both use them.

mgtkr1 · Post by **mgtkr1** » Sun Jul 06, 2008 11:37 am

janbros, its the shape of the rear boost port that allows use of tz piston were the pin is in the centre at the rear of the piston. i also beleive the yamaha pistons are able to cope with higher revs. so the balance is about right between the lower revs on the kr vs the location of the piston pin/boost port. its a good idea to keep an eye on them but as its a race bike there in bits more regular than usual so its possible to check things over. it depends on how well you stick to mantainance intervals, i know mj is less stringent these days and tbh i think you can get away with far more than you would expect. the chrome ''yz125'' ring has a much longer lifespan.

the-elf · Post by **the-elf** » Sun Jul 06, 2008 12:12 pm

Mat IIRC your now using a YZ piston. Which one do you use?

mgtkr1 · Post by **mgtkr1** » Sun Jul 06, 2008 12:56 pm

im using tz pistons in both these motors. one of which is 26j. the 26j piston uses a yz ring, very cheap and easy to get hold of. there chrome therefore have quite a good lifespan. the 26j piston however is becoming tricky to get hold of. my other motor uses 59w pistons and have a diffrent skirt cutaway. they weigh the same though so no problem with unbalancing everything. i think the 59w uses the quite easy to get hold of 1rk ring but i cant be 100% sure. for availability usingthe 4dp piston is the route to go but involves shortening the barrels. 26j and 59w are a straight fit with work on the head been the way to get optimum shape etc. also remember to drill the oilways on the ex side. i forgot once but still had no problem and the pistons still look new. just better to do it as the kips ports are close to the area and potentiolly an area vunrable to hot spots, esp if jetting is on the edge. i also use genuine kawasaki l/ends, circlips, gudgeon pin etc. apparently there lighter than the tz equivalants. does anyone know of a suitable yz piston? elf, this route (single ring) is definitly the best to take for ultimate hp as you can get more port area. they last longer than you think aswell. how often do you swap pistons or rings on std pistons?

kwackman12 · Post by **kwackman12** » Sun Jul 06, 2008 3:10 pm

Excuse my ignorance but can you use a chrome ring in a nicosil bore? or do u use liners?

mgtkr1 · Post by **mgtkr1** » Sun Jul 06, 2008 4:24 pm

yes you can use a chrome ring in nicasil bore. i dont have liners. id rather use good nicasil plating over liners. if i ever screw up a set of barrels i just get a set with good plating and copy the port dimensions. im not a fan of the liners but it is a good way of saving a set of otherwise good barrels. for road use i think liners are fine but for complete hammaering 70% of the time im unsure of how well they would fare.im no expert on this mind, the already borderline strength of kr barrels may be effected if more meat is removed to make way for a liner?

the-elf · Post by **the-elf** » Sun Jul 06, 2008 6:58 pm

mgtkr1 wrote: does anyone know of a suitable yz piston? elf,

Nope but I thought there was one that fitted and as the TZ pistons have almost disappeared, that was now the piston of choice.

this route (single ring) is definitly the best to take for ultimate hp as you can get more port area. they last longer than you think aswell. how often do you swap pistons or rings on std pistons?

That would depend on how often I get to race. If doing a full season, I would re-ring it half way though and new pistons at the start of the season. Got 4 new standard pistons left in the garage ATM.

BTW do you know what angle the squish band is for the TZ pistons? Save me working it out.

Cliff · Post by **Cliff** » Sun Jul 20, 2008 5:16 pm

Not able to make it this time, i'm helping a mate move house.
But i can run my bike down there anytime for a run.
I think it will do better next time!

More burgers for you lad's this year

.

kwackman12 · Post by **kwackman12** » Wed Jul 23, 2008 10:46 pm

Might be there on my zx12 but unable to bring the kr as BDK still havent done my crank & balance shaft yet! been nearly three weeks now

do they usualy take this long? when I phone up I only get to speak to the apprentice & no one phones me back

Got Cadwell booked on the 4th aswell, starting to get a bit pissed off with this