what would running 350 pipes on a 250 work like?

mboddy · Post by **mboddy** » Sat Jul 12, 2014 10:32 am

There are a number of books available that cover the subject of pipe design.
But if you want I can simplify it here.
The tuned length will determine whether it is a top end pipe or not. Shorter for higher revs.
Tuned length is distance from piston face to where the end cone would come to a point.
Shallower end taper is good for over rev. Steeper to stop it over revving.
More pipe volume will give wider powerband.
Multiple tapers on the header pipe will let you get the diameter and length of the body up to give you the larger volume.
It all has to tuck in and not scrape around cormers.

Greasemeup · Post by **Greasemeup** » Sat Jul 12, 2014 10:45 am

By your figures and Jerams guide figures, you would end up wit top end pipes if fitted on a 250cc then, happy days.

Sent from my iPhone using Tapatalk

Interesting reading here-

http://usa2strokers.com/forum/forum_pos ... tock-pipes

petegailey · Post by **petegailey** » Tue Jul 22, 2014 9:31 pm

As a novice who is doing some research trawling re the best pipe upgrade for my YPVS 250, this is what I've picked up so far. That many pipe sellers recommend the same pipe for 250 & 350 models. That different pipes are either better at hi rev or mid range depending on their volume. That its probably ok to fit a 350 pipe to a 250 but would become a high rev pipe? Have I got this right? Also it seems like pipes can be stainless steel, mild steel, aluminum.

I like the idea of using a 350 pipe in the event of miraculously sourcing a 350 head n cylinders from somewhere. (can anyone point me in the direction of a 350 top end?) ...then id have the pipes already on the bike..

I'm after a bike that spends more time ducking around 7000rpm than up around the red line. Jon reckoned that you get what you pay for with cheap pipes but I would like to find a good mid range pipe, both in performance and price. So in that scenario what brands should I be looking for?

mboddy · Post by **mboddy** » Wed Jul 23, 2014 10:00 am

I have a 350 top end. Bores look good. Only one piston. Head has some pock marks on one side.
I'll take some pics and you can make me an offer.

petegailey · Post by **petegailey** » Wed Jul 23, 2014 2:35 pm

Thanks mboddy, I'd appreciate that...

Greasemeup · Post by **Greasemeup** » Wed Jul 23, 2014 10:16 pm

There is a set of 350 barrels on eBay right now.

Crank & Gearbox internals as well.

petegailey · Post by **petegailey** » Thu Jul 24, 2014 12:15 am

Thanks greasmeup

2TInstitute · Post by **2TInstitute** » Thu Jul 24, 2014 12:39 am

JonW wrote:Im tempted to build a 250 RZ engine in my latest project. Ive never ridden one and those that do tell me they are a lot of run as the motor is revvy and long lasting (a factor of the piston weight and the crank/crankcase was designed for it of course). I believe they put out 48bhp vs the 350s 59-63, so none too shabby as standard.

I would probably fit PWK28s, dynatek coil and a programmable ignition for extra fun.

I have a set of hydroformed Gibsons that Ive never used but the seller told me they are race oriented with power up high and would probably use them on this build and wondered if Im being foolish or smart partnering high revving small ccs with a revvy pipe on a road bike, or is is that the larger 350 pipe would have some other effect on the power, and provide torque lower down?

Of course I also have a 350 top end as well, but I already have a 350 and a 421, I was just thinking I might do something different... happy to hear people's views...

250's are made to rev that's what the gear lever is for

. 1 tooth off the counter shaft is good for them as well. The 250 pipe would be better as it's shorter, still got those old RG pipes here in the trailer. BTW RG pipes 'work' because they are in the correct proportions. One of the best OEM pipes ever made. Problem is with early parralel twins with close bores centres it's possible to over scavenge the cylinder, 115mm for the belly dia is pushing it 110 mm is best.

mboddy · Post by **mboddy** » Thu Jul 24, 2014 9:33 am

I would take him up on the offer and fit the RG pipes.
They do work very well.

JonW · Post by **JonW** » Thu Jul 24, 2014 2:49 pm

They weigh a ton tho, but yeah compared to the RZ 250 pipes they probably weigh the same and go better

petegailey · Post by **petegailey** » Thu Jul 24, 2014 5:25 pm

2Tinstitute; pm sent.
pg

rz250rjapspec · Post by **rz250rjapspec** » Sun Aug 17, 2014 10:57 pm

Err.. They would be very, very loud!! Loud enough to raise an eyebrow or two from the local Constabulary!! Nah, just kidding, go on do it, you know you want to!!

JonW · Post by **JonW** » Wed Aug 20, 2014 1:46 pm

haha, too funny James!

2 Strokes Down Under