Team GPR

[mr bucketracer]

progress at last , a nice 12hp , spent the time and went over the engine , still running rich below 8.5k and up stairs , went crazy pulled out my rd50 to put back together , cheaked out the ports and timed it to that (-; , i'm shore with new pistion ring / fueling and maybe put something better than a mx ignition i hope 13.5 hp will be the go

[TZ350]

Real nice curve ....

[Bert]

That's looking heaps better...

[TALLIS]

12hp? Dammit, I'm playing catch up now. Time for the secret weapon

[mr bucketracer]

tweeked some more from it , still got that dam googleing at 8.5k( below and above runs mint) , ltfted and droped needle ,no fix , air screw , its like the transation from needle to main , kind of had a promblem like this years ago , i open carb to the port of doing it , held it there , killed engine and sanded some of the needle at that point , thing is i think its to rich there , i better have a good look at the a/f as its running as only records run from 8.5 when it breaks through

[mr bucketracer]

Real nice curve ....

it did not want to come easy , don't know how meany times i'v had it in bits )-; , i know you know the feeling , hows your reed cage one coming along

[TZ350]

The first one was a bust. The Team brought a good porting tool setup. Working on a second version cylinder now, will get to test it in a couple of weeks.

[mr bucketracer]

of the A/F it runs on the lean side of thing around 15 , but when it hits that 8 to 8.5k point its at 12.5 witch is rich , maybe i should try a smaller pilot jet , max hp is at 12.5 on the A/F , over rev runs up to 16 lean , its now on av gas running at 16 degrees , should i advance that ?now the fuel burns slower

[TZ350]

of the A/F it runs on the lean side of thing around 15 , but when it hits that 8 to 8.5k point its at 12.5 witch is rich

Interesting, because we often have a similar problem at much the same rpm.

You could try more advance, we typically run 26deg at 8.5k in the RG50's dropping of steadily to about 6 (from memory) at 12k.

Because yours sounds overly rich at that point as if the air is blowing back and forth in the carb picking up a double dose of fuel it might be worth trying changes to the inlet tuned length or try different reed valve petal material to change the reed resonance point.

Old Suzuki MX ignitions have a relativly steep retard curve. What was a sensible retard curve for a RM125 engines revving to 8K becomes very steep when run on a motor revving to 12-13k. We found we had to really advance the one on our engine up so the retarded ignition point at 11kish was in a sensible position.

Also we had a bit of an over compression issue (21:1) that held us up for a while, found lots of power when we checked the clearance volume and dropped the compression to 15:1.

[mr bucketracer]

good idea , will try the petals first , i had the same com as the gt50 14.1 , did not like it at all on this engine , its just over 15.1 now and gets runs that overlap each other so bloody good its not funny , found a bit on pipes i will post

[mr bucketracer]

i gave my gt50 chamber a quick messer up and found it very close to the one on here i copyed , only diffents was the belly is around 2 inchs longer on the gt , i tryed it before sorting engine out better ( i should try again), it made 4 hp more at 9000rpm and 1 less at the top , will copy and past this...(overlapping too much which would cause a canceling of their pressure differences)......thought somthing maybe conflicking at 8000rpm

[TZ350]

Interested to see how you get on, we are just beginning to look at understanding pipes, pretty green at the moment.

[mr bucketracer]

Interested to see how you get on, we are just beginning to look at understanding pipes, pretty green at the moment.

yes a bit to take in
http://www.dragonfly75.com/motorbike/ECtheory.html

[TZ350]

Thanks for that. We started by recycling a RG250 chamber on our Suzuki GP125 then used a RS125 pipe and that has served well for years. The RG50 got a pipe from Coker race products.

Chambers is quite good at actually making pipes, he has made copies of other pipes and from designs we found but now we need to get good at designing them too.

[seymour14]

http://www.ebay.com.au/itm/GPR-CUSTO...kAAOSwll1WuEGX

Them thars fighting words...