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View Full Version : 300 kits are no good, acording to Racing engine builder.



300rman
04-10-2008, 12:25 AM
well, talking to the PR Racing engine builder, the 300 kit for the 84 and under R are not too good. there were a ton of reasons that he mentioned, ill list a few major ones.

1. ignition on it is perfectly designed to run at the rpm ranges that the 250 runs at.
2. the 2 best performing overbores for the 250 cylinder are .40 and .60 over. the .20 is better than stock, but the RPM's drop significantly at an .80 overbore. when you get an even bigger bore (the 300) the rpms are even moreso drastically affected. not so much how high it rev's, but jut the way it comes up to RPM.
3. of all the ways to get power out of your 2 stroke, high compression and porting are the best machinist mods you can do. he doesnt like bigbores at all.

this is all from his mouth, not mine.
also, that little shop has close to 300 national top-performing motors that out-perform all other shops. both 2 and 4 stroke.
he likes Duncan for their motor work, and respects them. CT (i think it was CT) is a joke, according to him. and some of the best 2 stroke pipes are the PT pipes. thats the brand pipe he recommends all day long.

i must say, i was checkin out a MILD (he claimed was their mild) port job done to, what looked to be a 125 cylinder.......it was wild as hell. i mean he had more channels cut into the sleeve, and....it was very unique, and looked like a performer for sure.

they also have this nifty cylinder from a 125 from back in the day, before water cooling was a wet-dream. they went and made a water jacket of sorts around the cylinder cooling fins, and rigged up a water pump (didnt ask how), allowing them to run tighter tolerances in pistons, rings, bearings, and therefore to make more power. it looks very slick for sure.

i will say this. when it gets time to rebuild my top end, i will be taking him my motor and having him build her up.

the coolest thing i heard was that he can tell you your main jet size to within 2 or 3 sizes just by measuring the port timing.

had a guy get a shee built up over there. came to get it, took a test drive in the lot.....he put the bike through the front window of the business next door. :lol:



discuss above statements.

Jason Hall
04-10-2008, 09:35 AM
As you bore a 2 stroke cylinder, you change the port timing. If you look at the ports and how they exit from the cylinder, the exhaust port Is on a downward angle. This means as you bore over size you lower the exhaust port timing. This will change the engine's RPM range. The top of the transfer ports are also angled downward, some more than others. As you bore the cylinder over, you lower the transfers also. If you know this In advance, and the cylinder has the room you can modifi the port timings to keep your RPM range the same as stock. I believe that on some stock cylinders If you bore them to far, then sleeve them you take up ALOT of space/volume In the transfer ports. If you don't sleeve the cylinder, but Instead coat It with nicasil you might not affect the transfers as bad.

A big bored cylinder that Is built correctly should make better power than a small bore cylinder. A pro-x cylinder was built as a big bore cylinder, and I believe Is a awesome cylinder. I also believe that as you adjust port timing, you need to adjust your Ignition also.

ceaserthethird
04-10-2008, 05:55 PM
do you have a web site address for them ? ? ?

SYKO
04-10-2008, 07:54 PM
well seeing that the 300 kit was made by HONDA I think a bunch of enginers knew what it was capable of, I wont take advice like that.

1upfront
04-10-2008, 08:00 PM
well, talking to the PR Racing engine builder, the 300 kit for the 84 and under R are not too good. there were a ton of reasons that he mentioned, ill list a few major ones.

1. ignition on it is perfectly designed to run at the rpm ranges that the 250 runs at.
2. the 2 best performing overbores for the 250 cylinder are .40 and .60 over. the .20 is better than stock, but the RPM's drop significantly at an .80 overbore. when you get an even bigger bore (the 300) the rpms are even moreso drastically affected. not so much how high it rev's, but jut the way it comes up to RPM.
3. of all the ways to get power out of your 2 stroke, high compression and porting are the best machinist mods you can do. he doesnt like bigbores at all.

this is all from his mouth, not mine.
also, that little shop has close to 300 national top-performing motors that out-perform all other shops. both 2 and 4 stroke.
he likes Duncan for their motor work, and respects them. CT (i think it was CT) is a joke, according to him. and some of the best 2 stroke pipes are the PT pipes. thats the brand pipe he recommends all day long.

i must say, i was checkin out a MILD (he claimed was their mild) port job done to, what looked to be a 125 cylinder.......it was wild as hell. i mean he had more channels cut into the sleeve, and....it was very unique, and looked like a performer for sure.

they also have this nifty cylinder from a 125 from back in the day, before water cooling was a wet-dream. they went and made a water jacket of sorts around the cylinder cooling fins, and rigged up a water pump (didnt ask how), allowing them to run tighter tolerances in pistons, rings, bearings, and therefore to make more power. it looks very slick for sure.

i will say this. when it gets time to rebuild my top end, i will be taking him my motor and having him build her up.

the coolest thing i heard was that he can tell you your main jet size to within 2 or 3 sizes just by measuring the port timing.

had a guy get a shee built up over there. came to get it, took a test drive in the lot.....he put the bike through the front window of the business next door. :lol:



discuss above statements.

No good my *ss This guys just being nit picky, now don't get me wrong I'm sure his company does excellent work but I've proven on the track that 300r's can be very potent. The 300r kit's purpose was simple bolt on power utilizing the stock bottom end nothin bad about that right.

300rman
04-10-2008, 08:38 PM
No good my *ss This guys just being nit picky, now don't get me wrong I'm sure his company does excellent work but I've proven on the track that 300r's can be very potent. The 300r kit's purpose was simple bolt on power utilizing the stock bottom end nothin bad about that right.

i guess what he is saying is that he could make a 250 top end run better than a fairly worked over 300, and it would rev better all day long.

i guess his world is Racing, where high rpm is where its at.


im not saying there junk,i love mine. jut figured i would share the thoughts of someone outside the trike world i guess.

something else he mentioned, making the head dome larger and narrowing the squish band to keep the same compression also makes a huge difference. can anyone collaborate?

lndy650
04-10-2008, 09:12 PM
you should defenitly rechamber the head with a oversized piston.its not always a must but it will make the engine perform better.