RZ250R conversion project to be an RZ350R

[Phantom]

So I managed to get a good priced RZ250R to someone whose trying to rip me off saying its an RD/RZ350R and wanting me to pay high fortune for it, so I was personally checking the bike further as the basic and checked the Frame chassis and engine number and immediately find the starting numbers with 29L stamped did some searching on the internet and some asking to some friends who know more 'bout Yamaha 2 strokes and was confirmed that the bike that is being sold to me is indeed an RZ250R and not an RD350 that is being advertised by the owner himself. Long story short we both agree on inking the deal that is agreeable in both ends, got me an RZ250R and he got his money, both of us return to our caves with a printed smile on our face.

So I wanted to know what will be the necessary parts needed for the conversion to make it an RD/RZ350 itself and what are the parts I can reuse or need to replace?

[tacky1]

I believe you need the pistons, cylinders, head and oil pump. Rejet the carbs. I’m not 100% on the exhausts.

[Phantom]

I believe you need the pistons, cylinders, head and oil pump. Rejet the carbs. I’m not 100% on the exhausts.

Interesting, I was checking net for more info but most of them are outdated so I wanted to ask for an up to date conversion method.

[silverstrom]

Follow Jon's RZ250 conversion here viewtopic.php?f=5&t=4650

From Jon's website, this is the conversion parts list. http://2smoked.com/Yamaha_1985_RZ250_to ... rsion.html

Contact him if you have questions. I'm sure he'd be happy to offer advice.

[MK]

There's a couple of alternatives to 350 cylinders.

1) Why not ride it as a 250 first? Give it a try and you may like it.

2) Banshee cylinders will fit, but stock banshees will have about equal performance to the 250 YPVS.
You could get a cheap set from Alibaba and port them.
https://a.aliexpress.com/_mP9yGAX
You'll need to fabricate an adapter for the pipes as the banshee has a different flange.

3) Any aftermarket banshee stuff will fit, too.
The Athena kit is the lowest price per hp.
https://www.athena.eu/en-us/big-bore-cy ... P20737.htm
You can get into the 80'ish hp with these.

[Phantom]

There's a couple of alternatives to 350 cylinders.

1) Why not ride it as a 250 first? Give it a try and you may like it.

2) Banshee cylinders will fit, but stock banshees will have about equal performance to the 250 YPVS.
You could get a cheap set from Alibaba and port them.
https://a.aliexpress.com/_mP9yGAX
You'll need to fabricate an adapter for the pipes as the banshee has a different flange.

3) Any aftermarket banshee stuff will fit, too.
The Athena kit is the lowest price per hp.
https://www.athena.eu/en-us/big-bore-cy ... P20737.htm
You can get into the 80'ish hp with these.

might be a good Idea but since I wanted to up bore it up to 350cc is a better Idea :)

[JonW]

Does amuse me that people think a 250 is some kind of rip off, probably these days an actual 250 is probably rarer lol

Ive no idea where the OP lives but if its a JDM RZ250R its probably a 51L cylindered bike. Feel free when you junk those cylinders to send them boring ole paperweights to me :)

The 51L has an extra (boysen) port that no other RD/RZ cylinder has and pipes/CDI/Carbs to match. it makes good power and revs for days as the engine is actually designed round the 250 size, not 350. pics of those ports on my 251LC build.

I agree with Martin, why not ride it as a 250 and see what you think?

The RZR also is full faired 1985 bike, if you live in the USA it would be rare cos of that by itself. In Canada the fact its a 250 makes it super rare. If youre in the UK, same thing. If youre in Aus then we had more 250s than 350s in 85 and ours are not 29L, so yours is an import. All that said, I bet you tell us youre in NZ... haha.
EDITED: Ive seen you are in the the Phillipines. Cool. Ive no real idea what bikes or the spread of them for your market, but i reckon this bike is an import. We need pics...

I also wrote a big bore primer on my site for those wanting to go for bigger cyls. Its all fits on the same 250 bottom end of course.

My website is now in limbo, the site builder software died last year and is long not supported and it corrupted the local files. I then stopped paying the bill but the hosting company never deleted it. Some bits no longer work which is fine, but the info is still useful Ive been told so Ive made no efforts to remove it.

[kpke]

2) Banshee cylinders will fit, but stock banshees will have about equal performance to the 250 YPVS.
You could get a cheap set from Alibaba and port them.
https://a.aliexpress.com/_mP9yGAX
You'll need to fabricate an adapter for the pipes as the banshee has a different flange.

Martin, do you know anyone that has used those cheap banshee kits?

There's a YouTube porting guy that says they're okay but not surprisingly it can be a bit of a crapshoot. Sort of tossing the dice that you get parts that are decent quality. Just curious.

[tacky1]

2) Banshee cylinders will fit, but stock banshees will have about equal performance to the 250 YPVS.
You could get a cheap set from Alibaba and port them.
https://a.aliexpress.com/_mP9yGAX
You'll need to fabricate an adapter for the pipes as the banshee has a different flange.

Martin, do you know anyone that has used those cheap banshee kits?

There's a YouTube porting guy that says they're okay but not surprisingly it can be a bit of a crapshoot. Sort of tossing the dice that you get parts that are decent quality. Just curious.

Kevin Herr uses them on his Banshees Ken, Reckons the cylinders are great, pistons are junk though, He tunes the crap out of them for alcohol motors and dune racers and drag motors with long rod conversions and never had a prob with them.

[kpke]

Phantom, sorry to jack your thread.

Paul, that's who I was talking about. I've watched several of his videos

I would still like to hear if Martin has any experience with these cheap banshee parts.

[MK]

Martin, do you know anyone that has used those cheap banshee kits?

There's a YouTube porting guy that says they're okay but not surprisingly it can be a bit of a crapshoot.

Yes, I recently spoke to a German Banshee guy who confirmed that the cylinders were not too bad but need to be ported / altered for performance.
Definitely a good bang for the buck relation.

[Phantom]

Phantom, sorry to jack your thread.

Paul, that's who I was talking about. I've watched several of his videos

I would still like to hear if Martin has any experience with these cheap banshee parts.

No worries, its additional info about the topic so its all cool

[kpke]

Martin, do you know anyone that has used those cheap banshee kits?

There's a YouTube porting guy that says they're okay but not surprisingly it can be a bit of a crapshoot.

Yes, I recently spoke to a German Banshee guy who confirmed that the cylinders were not too bad but need to be ported / altered for performance.
Definitely a good bang for the buck relation.

Thanks Martin. Good to hear. I have a 421 build coming up but I doubt I will take that chance.

[MK]

Compared to ported stock banshee cylinders, the 421 kits (either Athena or CPI) would be the easier & better choice as they have auxiliary exhaust ports that the stock ones lack.
(Note that for 421 you need a plus 4 crank in addition)

Cost wise the Alibaba kits are cheap as chips. That's why I suggested them to enhance a 250 engine with a low budget.

[kpke]

Compared to ported stock banshee cylinders, the 421 kits (either Athena or CPI) would be the easier & better choice as they have auxiliary exhaust ports that the stock ones lack.
(Note that for 421 you need a plus 4 crank in addition)