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Will this buff out?

Started by teazer, February 11, 2019, 01:19:37 PM

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teazer

 ??? :eek:

Jspooner

sand it smooth with some 400, unstick the rings and run it. It'll be fine.  :haw:
"Just quit brain fucking it and get it done"

teazer

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.

teazer

Quote from: Jspooner on February 11, 2019, 01:29:40 PM
sand it smooth with some 400, unstick the rings and run it. It'll be fine.  :haw:

That's what I was thinking Joe.   ::)

retaRD

Is there any difference between the R5 and RD350 standard head volumes?  I always figured they were the same head.

teazer

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.

retaRD

I have a set of stock RD350 heads I should measure, but for some reason I remember it being about 22cc

SUPERTUNE

20.5cc is too small for todays pump gas for sure...(well you could if you took out good ignition timing for way retarded timing and make it even more of a pig off the bottom end power).
Some RD350 stock heads came with 22.0 and 23.0 CC heads.
The step of the squish tells the differences on these stock ones. like .022 on the 23cc and close to .011 on the 22cc heads.
350's have horrible squish clearances and in the old days we just milled the piss out of them even letting to squish OD get a little smaller just to get to .042-.046in. Back then in the day we had good leaded fuel.
It did increase the squish ratio to over 50% too and can be hard to make live at wide open hard throttles with the pump fuels today. I like no more than 45% max. more like modern designed 2 stroke chambers.

I like to try and alway use the later model RD wavy heads and not the R5 type shark fin heads when you can, as the shark fin heads have been known to crack when milled.
IMO, doing a RD400 .020in. headgasket conversion and re-machining the heads is the way I mostly go. Another reason is I can use a higher head bolt torque value to prevent headgasket failures that the 350's are prone to have with the .040in. thick ring gaskets.

Scott C. has a nice way of re machining the stock heads with a step in them  and oring to not use the crappy RD350 .040 ring gasket.
With this method it get the squish band down closer to the piston.
But have you still have to manage the squish ratio and compression ratio.

Chuck
RD machine work, boring, porting, cranks and engine building.


Chuck 'SUPERTUNE' Quenzler III
Team Scream Racing LLC
1920 Sherwood St. STE A
Clearwater, FL. 33765
cqsupertune@tampabay.rr.com

teazer

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.


teazer

So I put it together with ported cylinders, milled cylnders, YZ85 reed cages and reeds, 400n head gaskets, Lomas pipes and it runs extremely well. Jetting was as advised by Chuck Q and to my surprise it fires up first kick and has a flat linear powerband. 

Peaked at 52hp at 9,000 and 30 ft pounds to torque at 8600.  Air to fuel is slightly lean off idle suggesting it needs 2.0 slides and top end is slightly rich with 220 jets.

Could not believe how cleanly it picks up throttle and how flat the power curve is from 6 to 9.  Nice curve, not steps. No power below 5000 maybe 5500 but it runs cleanly down there - just no one at home.

Very happy the way it turned out.  There's more in there I'm sure but happy owner.  Happy dyno guy, so I'm OK with that.  Next i need to try our tame drag bike and see what it makes.

 

SUPERTUNE

Sound great...Yeah if your on the stock 28's with the primary needle jet conversion, it will be real rich on 220's, drop in some 200's and it will really light up some extra topend pull...
Chuck
RD machine work, boring, porting, cranks and engine building.


Chuck 'SUPERTUNE' Quenzler III
Team Scream Racing LLC
1920 Sherwood St. STE A
Clearwater, FL. 33765
cqsupertune@tampabay.rr.com

teazer

You are spot on Chuck.  We could see from the Air:Fuel ratio that it was rich all the way on the main jet and the fuel curve was fairly flat. It got marginally richer as revs rose ( on full throttle) so I'm happy that you told me to cut down the spray bar, or else it would have gone from rich to super rich.

I decided to leave it rich to be safe.  The owner already texted this morning to say that on the street it is scary fast.  Way more than he was expecting.

How long before he calls back looking for more.... :whistle:  As they say, too much is never enough.

As long as the drag motor makes more power I'll be happy. We're starting out with a more or less stock 750 top end but I need to build the 400 with wild porting as soon as I design some bigger reed houses to take some large 6 petal reeds from something a bit bigger.   :eek: