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Thanks.  TZ's use O-8 so P-0 makes sense.  I decided to start rich because it's not my bike and a couple of jets are cheaper than rebuilding it again. I'll order  a pair of P-0s.

Interesting that the R5 used O-0 but without reeds I would expect more reversion and more fuel as a result, so with a reed motor, slightly richer needle jet seems logical.

I know this was covered many times on the old board but since I can't search that, I thought I'd start a new thread.

RD350 with ported OEM cylinders, YZ85 reeds, Banshee cross linked inlets, 6mm spacers, RD400 head gaskets, stock 28mm carbs, JL stainless pipes, Y boot with tall K&N filter, DYNA ignition.

Carbs have been stripped and cleaned and drilled and tapped to take air jets.  I am thinking as a starting point (should be on the safe side)
Main jets:   220
Needle:      5DP7-3
Needle Jet: 169 P-2
Pilot jet:      32.5
Air jet:           2.0

I read Dale Alexander said that he cut the spray bar down to 2mm but I didn't see that mentioned in a copy of the Dave F instructions. I am pretty sure that I saw Chuck Q recommend that in the past and he knows what works.

Any thoughts, comments or recommendations?

Thanks

That's a great question.  I'd speculate that most guys there run stock or mildly modified bikes and that the stock reeds may well be adequate for a mild or stock motor.  A high performance motor is probably restricted in the reed area and a bike with large carbs can probably benefit from better flowing reeds, but small stock carbs on a mild motor probably don't need more reed area.

Some years ago Performance Bikes tested a bunch of different reeds and cages on an LC cylinder and the difference in HP and flow was barely measurable.  That may have been on a fully tuned 250 though.  I can't remember and it's too cold outside in the shop to go and dig it out.

So the question that raises is at what HP or airflow level do the reeds become the limiting factor?

That looks really nice John - reminds me of a Suzuki Stinger but with more pronounced style lines.

Brandy Red.  Great color but the clear coating flakes off.  I have one in the shop right now for engine rebuild.

I suspect that you might be rich in the midrange ie mid throttle.  Others use P-2 or P-6 needle jets with 6DH7 needles which are leaner.  6DH3 taper stats earlier and therefore is smaller from that point on, even with the same taper angles.  But try it and see how it runs.

#270 is a fairly small main jet, and maybe it's compensating for the needle and jet combo up to flat out. Or maybe it's the right amount of lean out to match the lower altitude.  Honda suggest one jet size decrease for that altitude, but that's for their generators with tiny jets. ROtax suggests a 7% reduction for that altitude, so that's say 320 down to 300 (298 to be precise, but jets that size don't exist).

The thing is that cold air is denser and high altitude air is less dense, so it's always a compromise.  At 60 degrees it's about a 7-8% reduction and above 12,000 at say 80 degrees it's a 13% reduction.  In a low pressure trough, it will be an even larger decrease. 

I'd start with 300 mains, P-6 needle jets and 6DH7 needles but start rich and see how it runs and then try to lean it out a little at a time.

With carbs off teh bike as someone already commented, set fuel level to 3-4mm below the gasket surface on both carbs.  Job done.

When I weighed a bunch of conventional forks a few months ago FZR400 were the lightest by quite a margin and with an alloy stem and/or alloy bottom clamp, they could be even lighter. I have a modified GSXR stem in a set of RD350 forks on the drag bike.  That saved a bit.

Might be worth looking at a modern small bike for even lighter/stiffer forks.

Yes, the second video listed. The fuel filler is from Aircraft Spruce. A bond on or bolt on. :)

Thanks John,

That is one sh!t load of work.  Thanks for sharing. 

Thanks Chuck. The stepped head idea (the other way round, used to be common on British singles.  The Goldie came with a multi layer head gasket that had to be peeled off to get the right seal on the lower and upper steps. I did think about doing a stepped head but the tolerances on Vito's and OEM barrels are not perfect, so I'll take your advice and machine the step off and use a thin RD400 gasket.    Heads will still need to be machined, so I'll send them to you soon.

Took me a while for the seizures to stop.

Do you have a slightly slower version that shows the steps you have to take, such as the flange down the spine and the tunnel and bungs and filler cap? That would be instructive to many of us that might think about making a one off tank but probably never will.

I think you are correct.  I dodn't happen to have any RD350 heads other than the pair that arrived on this bike.  The R5 heads I do have came off a TR3 replica and have a very different shape with flat roof.  I was surprised that both measure out to the same volume since one set had supposedly been reprofiled for racing and the other set is supposedly stock (and I have no reason to think they are not).

20.5cc seemed a little low but I have no other heads to compare with other than Banshee domes or TZ heads.

sand it smooth with some 400, unstick the rings and run it. It'll be fine. 

That's what I was thinking Joe.   ::)

Back story: Bike had been in storage for decades and had been cleaned up and looked pretty good.  It's a really early RD350 that had been fitted with VITO's barrels and OEM 1A1 pistons, but the crank seals were original and leaked. On top of that the reed cages leaked slightly and carb circuits were partially blocked so the poor thing didn't stand a chance - but it did look good. The new owner fitted a pair of Jim Lomas pipes which are absolutely the bee's knees.

I did run a bunch of numbers through MOTA with different port specs and whatever I do, those pipes make a lot of top end and lose a lot low down, so I tried to come up with port specs that give the most overall.  The liner to barrel interface is better than the VITO's barrels but still left a lot to be desired, but it's better now than it was. The rear (auxilliary) transfer ports are tiny little things though.  What a PIA to work on even with a decent angle head porting tool.  I had a pair of YZ85 reed cages so that meant lots of quality time porting to get them in.

Crank was rusty and has been replaced and a set of OEM barrels with stock bores procured, ported, blasted and painted. Will drop them off for reboring later. Interesting that one of the VITO's barrels was about 20 thou short which doesn't help.  cases were vapor blasted, cleaned and sealed with clear. 

Clutch had a lot of back and forth play, so it was stripped and the cush rubbers replaced.  They were mainly undersized and two had completely disintegrated.

Heads measured out at around 20.5cc which is the same as a set of R5 race heads I had lying around, so they will have to me machined by someone.

 ???