R5 -RD350 conversion

[Still biking]

Years ago I bought a bunch of parts and engines from a very experienced RD person who raced and rebuilt bikes  and it included the following item.  It was an R5 engine rebuilt with RD350 cylinders (ie reed valves).  What piston would be used in that unit to have the correct compression ratio?  It has .75 over pistons when I take the head off.  Could an RD350 piston be used in such a set up?   or does the height of the top of the piston to the wrist pin differ between the R5 piston and the RD 350?

[Jspooner]

He should have used RD pistons.

[m in sc]

r5 and rd pistons are pretty much identical aside from the rd ones having the boost port windows in the intake face.

[Still biking]

Can you just bolt up an RD top end ( RD cylinders, heads, pistons, carbs, etc) or do you have to do modifications to the pistons or cylinders to make that work?  I am wondering how modified the parts that are on this engine may be.

[m in sc]

bolts right on. no mechanical mods needed.

[ADW]

bolts right on. no mechanical mods needed.

I'm stuck on the other side of this question. I had to have the cylinders for my 71 R5B bored out to 65mm. I found some 65mm pistons and rings in a website from a 2-stroke company that said they also had R5 parts. I can't necessarily say that the information was a little confusing...they didn't specifically say the pistons and rings I was buying would work for R5, but I didn't know any better. Anyway, I bought the RD pistons and ring sets and installed them yesterday, not knowing for sure whether the holes in one side of the pistons would only work with an RD/Reed Valve cylinder.

Thankfully I found info about the holes on the pistons would NOT work properly with my R5, so now I'm searching for a  two 65MM piston and ring sets specifically for a R5. Do I have a chance in h&ll of finding them? 

[1976RD400C]

Wossner makes R5 pistons up to +2mm.

[AAAltered]

Wow. 
- So HVC was repopping, I don't see them on their site any more.
- HVC shows a set of Wiesco+1.0 in stock but they MAY need a different bore clearance than yours.
- Yambits OEM and Wossner are out of stock.
- Economy doesn't show any but you should at least call John and ask.
- One Ebay seller appears to have a complete Wossners +1 set.  Search out seller bikebuzzard2.

Many of us went through an R5 piston drought in the 00's, then some reproduction (Wossner, HVC...) and OEMs starting showing up from peoples stashes.  Seems like we are back in a drought.  My +.75 HVC top end has about 3000 miles on it.  Fingers crossed.

Good luck.  Keep searching.  They exist.

Keep in mind that some markets including th UK called them YR5's...

[m in sc]

the only size Yambits doesn't have on hand right now is 65mm, but they will im sure be back soon.


https://yambits.co.uk/pistons_and_parts_for_yamaha_yr5.html