Yamaha rd350 Road Racer Liquid Cooled!!

Re: Yamaha rd350 road racer

teazer said:
Great book. That man was ahead of his time in many ways. Of course, things have moved on since then and there is more knoweldge in teh pool to dip your toe.

A.G. Bell is a good read - probably easier to read.

Q: do you plan to race it, do track daze or just ride it hard and put it away wet? If it's for teh race track, race gas is a good solution but you don't need super high octane levels. C12 is fine for most things. My race GT750 will run happily on 93 octane street gas but I have run it on U4.4 (wow) and set a new personal best with a drum of old C11 pre-mix.

For a high comp race type motor C12 is fine.
I'll look into that other book as well!

The plan is for a street toy bike. I'm not a skilled enough rider for track days or racing. The goal is for the longest trip to probably be the pass from where I stay at barber to the show itself. I'm guessing a 15 mile stretch at best.

Something to zip around here and put away wet, or make the whooping 4.5 mile ride into work now and again, but as I said, a street toy, not a daily rider

Also, as my fuel ignorance will show, what's c12. Thinking through it again, I'd probably be best off to seal the tank and be able to run on 5% ethanol 93 octane pump gas
 
Re: Yamaha rd350 road racer

Levi, when you decked your cylinders for the O rings I am assuming that you removed the indent for the original gaskets? That right there was a step in the right direction to fix the squish.

Sent from my SAMSUNG-SM-G920A using DO THE TON mobile app
 
Re: Yamaha rd350 road racer

That's good to hear. The objective is a bike that is fun to ride. Light and good brakes and exciting street performance. So we are looking at mild porting with say slightly taller and wider exhaust port, stock transfer ports and cleaned up inlets with better reeds. Could be OEM with YZ125 reed petals or YZ85 sided single petal reed cages or even Banshee/RZ350 reed blocks. Nothing outrageous.

Slightly higher that stock compression but nothing outrageous and an O ring head/barrel seal with heads centered on the bores. 93 octane street gas should be sufficient for that combo. Clem is right about squish and head machining.

Just for the record:
VP race fuels
https://vpracingfuels.com/racing-fuels/

http://www.racefuel.com/vp-c12-racing-fuel-108-octane/

http://www.racefuel.com/vp-u4-4-racing-fuel-103-octane/

http://www.racefuel.com/vp-101-street-legal-unleaded-101-octane/



Sunoco

http://www.sunocoracefuels.com/fuels/compare-fuels

http://www.sunocoracefuels.com/fuels

And just to put it into context: https://drive.google.com/file/d/0B7r8KNzyxX04WklDQTZDYnFyblE/view
 
Re: Yamaha rd350 road racer

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Re: Yamaha rd350 road racer

Bet you cant top this
 

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Re: Yamaha rd350 road racer

clem said:
Levi, when you decked your cylinders for the O rings I am assuming that you removed the indent for the original gaskets? That right there was a step in the right direction to fix the squish.

yep, on my first try I did just as you said, however, im gonna grab a new set of barrels, as one of mine is on its last over bore, and im thinking about going a little different with this one. I think instead of taking the lip out, I am gonna leave it there and instead of dowelling the head to the barrel, I will cut a raised lip in the head for alignment, similar to what dg did with their sunburst heads..

any thoughts on that would be helpful..

teazer said:
That's good to hear. The objective is a bike that is fun to ride. Light and good brakes and exciting street performance. So we are looking at mild porting with say slightly taller and wider exhaust port, stock transfer ports and cleaned up inlets with better reeds. Could be OEM with YZ125 reed petals or YZ85 sided single petal reed cages or even Banshee/RZ350 reed blocks. Nothing outrageous.

Slightly higher that stock compression but nothing outrageous and an O ring head/barrel seal with heads centered on the bores. 93 octane street gas should be sufficient for that combo. Clem is right about squish and head machining.

Just for the record:
VP race fuels
https://vpracingfuels.com/racing-fuels/

http://www.racefuel.com/vp-c12-racing-fuel-108-octane/

http://www.racefuel.com/vp-u4-4-racing-fuel-103-octane/

http://www.racefuel.com/vp-101-street-legal-unleaded-101-octane/



Sunoco

http://www.sunocoracefuels.com/fuels/compare-fuels

http://www.sunocoracefuels.com/fuels

And just to put it into context: https://drive.google.com/file/d/0B7r8KNzyxX04WklDQTZDYnFyblE/view

I already have a set of yz125 reed petals in the shop waiting, as well as a banshee manifold with a crossover tube. I still have your notes on ports as far as the pipes that you ran the numbers on for me (thanks again).

Also, as that goes, ive been scouring the net and asking around about the Rajdoot barrels that are coming up online. They are cheap and I could put together a top end with those barrels and prox banshee pistons (with the tang removal) for half of what the vitos kit is...

I guess what im thinking, is that if im having porting done anyhow, why not start with the indian de tuned jugs......

again, any advice would be welcomed ;)
 
Re: Yamaha rd350 road racer

I like the idea of setting the head into that recess with O rings to seal them. That's what I plan on doing with mine, but I need to be really careful that the two steps are right. Problem with a stock 350 arrangement is that the head bows as it's tightened down over the head gasket. Mine will have to be machined out of billet blocks 4" x 4" x 1.5" so I can use TZ aluminum head bolts/nuts.

ebay has some Chinese made new RD350 barrels for 150 shipped per pair. Mine were damaged in transit and have slightly bent fins, but the casting work is amazing. That said, the ports need to be cleaned up somewhat to get them where you want them.

Another possibility is to bore yours to 66mm and/or have them nicasil plated like a TZ except the plating is on the liner and not on bare aluminum.

Choices, choices... Did you read the safety sheet on that race gas? It's scary shit..
 
Re: Yamaha rd350 road racer

bradj said:
Bet you can't top this

Been there, done that. - once or twice or 4 times at Daytona - turned out to be the tiniest minor air leak between inlet manifold and barrels.
 
Re: Yamaha rd350 road racer



teazer said:
I like the idea of setting the head into that recess with O rings to seal them. That's what I plan on doing with mine, but I need to be really careful that the two steps are right. Problem with a stock 350 arrangement is that the head bows as it's tightened down over the head gasket. Mine will have to be machined out of billet blocks 4" x 4" x 1.5" so I can use TZ aluminum head bolts/nuts.

ebay has some Chinese made new RD350 barrels for 150 shipped per pair. Mine were damaged in transit and have slightly bent fins, but the casting work is amazing. That said, the ports need to be cleaned up somewhat to get them where you want them.

Another possibility is to bore yours to 66mm and/or have them nicasil plated like a TZ except the plating is on the liner and not on bare aluminum.

Choices, choices... Did you read the safety sheet on that race gas? It's scary shit..

I'll have to do a bit more o ring research, but my plan is that the mating surface on the head and the o ring step is a precision match, or about .001" less so that the head sits flush where the bolts draw it down and does not bow like the stock setup does... Also, that way I can bolt those heads onto different barrels without having to mod the barrels themself if need be.


If you are saying the Chinese jugs are suitable for use, that's good enough for me, as long as they can be ported to spec without much issue.. I'd rather stay away from the cost of nikisil and start with a fresh set of barrels if I can.... I'm also still thinking about making some billet water cooled heads in the future, perhaps that are adapted to use banshee cool head inserts... That's down the road though. I know a company did it back in the earlier years (I think the name was revco??) But they didn't use a water pump, it was a thermo siphon deal. I was thinking about using a tz water pump in place of the oil meter, or von yinzer also mentioned an electric water pump. He also mentioned that water cooled heads may not be an upgrade unless jacketing the barrels as well... At which point I would guess finding a 350 lc top end would be a far better option anyhow.


I need to look at that sheet on the race gas, I didn't get to that yet today lol
 
Re: Yamaha rd350 road racer

Water cooling is a great upgrade for a bike that is ridden really hard or in unbearable heat, but for what you describe, may not be so necessary (or cheap). I would stay away from TZ parts except to see how they were designed. Port shapes are old school and so are teh large water passages. An LC top end would be nice insurance, but not cheap and needs a water pump and radiator etc. Water pump can be TZ style or LC/RZ style or electric. There's a reasonably priced Bosch unit for VW's and Audis but unless you have the spare dollars burning a hole in your pocket, maybe just keep an eye open for an LC350 top end during the off season.

I have a few hours into porting a set of Chinese barrels and no way to know if the metal is cheesium until I run them in anger. I read somewhere on another forum that RD350s have thinner liners than an RZ and cannot be bored as large, but I don't have that reference. If possible, use the barrels you have.
 
Re: Yamaha rd350 road racer

I think you will find that the bending issue with the heads pretty much disappears with the o-rings. If you machine the head to look like it has a permanent original copper gasket than certainly the bending effect will still be present as the bolt holes will still overhang contact surfaces that hold the o-ring. This presumes you leave a space between the cylinder and head where the bolt passes through. As long as you don't over torque the head nuts, the o-ring should still seal. If you machine the heads so that the height of the step is the same as the old gasket recess, then the bending problem disappears and you now rely on the beam strength of the head between the bolts offering sufficient clamping pressure. Which is what you do regardless - but you will be eliminating the problem that exists with the stock arrangement. If you are facing off the top of the cylinders, keep the old gasket recess as shallow as possible - you only need it to be deep enough to register the new flange you are machining into the heads. Keeping the recess and the corresponding flange as shallow as possible will let you machine the least amount of material off of the heads. You want to keep the heads as thick as possible to end up with the maximum beam strength.
 
Re: Yamaha rd350 road racer

You could always set up you cylinders to use the RD400 gaskets too.
One thing on the overseas cylinders that may be a little insurance is to pin the sleeves to the cylinders. The Internet says that they may move around in there. Teazer may know for sure pretty soon and he will be able to enlighten us all.

Sent from my SAMSUNG-SM-G920A using DO THE TON mobile app
 
Re: Yamaha rd350 road racer

I'm thinking that I'll go with the centering design using a step turned into the head with the same height as the depth of the step in the barrel. As far as making the step as shallow as possible, all of the stock barrels that I have at the moment set right at .027" from the top down to the stock gasket surface (measured with depth micrometers). I don't know that I'd want to use much less of a step than that to register it? Maybe cut it in half and use .014" or so, but that's getting to be a pretty miniscule amount id think, and I'd worry about the the o ring itself holding it up too high until it is torqued into the centered position.

I also re made my arbor to do the head machining on. I wasn't super happy with how my first one turned out, so I made another one the way I should have in the first place, by single point threading instead of a bolt drilled and tapped into the arbor itself. (It's nice having a friend that lets you use his mill and lathe. My old south bend doesn't have metric thread pitch change gears)
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I went ahead and milled the spark plug surfaced to insure that they are parallel to the gasket surface. I only took about .003", just enough to clean them up.
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The heads have been warped at some point as shown by an indicator. They vary by about .004" on the indicator, but that can be fixed when turning.
573ef0dcff57f5f4c5c1b958712a82a5.jpg


I was also going to pick you guys brain on rd250 heads. I have a set here that I could machine to suit, and being as they have a smaller combustion chamber, I'd have more material to shape the squish/ combustion chamber to whatever need may be. The only thing I'm not sure of is whether they have the same amount of material as the 350 heads and if not, will machining them to the specs needed will remove to much weakening them. Any insight would be much appreciated.

Also, I'm itching to work on this thing, but I have more ambition than cash at the moment. I picked up an rd250 bottom end recently with a descent crank in it. I'm not planning on running that crank as it would need rebuilt, so I'll probably still go with the vitos unit, but the question is, can I use the crank to setup my top end (squish) and then still have the same results when I rebuilt the bottom end with a new crank, or should I just wait until I can fork out the cash for a crank as well. I'm just not able to bite the bullet and buy a crank AND a top end right now, but I have a little time on my hands, at least at the moment ha
 
Re: Yamaha rd350 road racer

the 250 and 350 cranks are identical. 250's have a larger ratio primary drive, so you have to swap out the gear, but the actual cranks are the same. Nice machine work! I've never measured how much the o-ring holds the head off the cylinder, but it is very small. Feels like nothing when assembling, but as you point out, the full step is quite small anyway so making is smaller is a pretty small gain.
 
Re: Yamaha rd350 road racer

Nice work. I may have to send a set of heads for you to machine for me... :)


I've never measured how much the o-ring holds the head off the cylinder,...
Should be zero. If not, it won't seal properly.

The ring is round in cross section and it deforms into the groove which has a square cross section. Any pressure that leaks in there should cause further ring deformation to maintain the seal.

The seal groove must be square. Do not try to make it round and expect the O ring to sit in there and seal it off. I "inherited" a set of expensive heads like that that leak profusely as they blow out seals. The domes/inserts will have to be redesigned to make them work.
 
Re: Yamaha rd350 road racer

teazer said:
Should be zero. If not, it won't seal properly.

The ring is round in cross section and it deforms into the groove which has a square cross section. Any pressure that leaks in there should cause further ring deformation to maintain the seal.

The seal groove must be square. Do not try to make it round and expect the O ring to sit in there and seal it off. I "inherited" a set of expensive heads like that that leak profusely as they blow out seals. The domes/inserts will have to be redesigned to make them work.
Indeed! to clarify, I was meaning the distance the ring sits proud of the groove with the head off. I guess easy enough to know by subtracting the groove depth from the ring dia.
 
Re: Yamaha rd350 road racer

I need that test indicator. You and your fancy measuring devices. 8)
 
Re: Yamaha rd350 road racer

Fantastic discussion gentlemen. All I'll add is that I worked on a set of the India made cylinders back in 2010 for a customer and one of the sleeves was offset to the port castings by several mm. I can't recall just how much, and the porting requested took care of the issue anyways. QC may have improved since then though. Oh, and they shipped two left cylinders initially. Oops.
 
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