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Aircooled RD Tech Help 250cc and Above / Cold side...
« Last post by 44Dwarf on Today at 12:46:37 AM »
Hello All.
I've got a 74 RD350 race bike. Fresh crank and new top end. Noticed the last race the left side points had started to close up a bit and the cyl was a bit cooler then the right. Knowing the sources for high quality points and condensers theses days is not good i installed a HPI 210 mini exterior rotor kit.
Brought the bike to the dyno and the left is still colder then the right.
I'm loosing my mind trying to figure out why.  Things checked so far.
4 sets new plugs.
New reeds
Compression is a tick over 125PSI both side hot and cold.
Cleaned carbs one at a time. probed all passage ways, compressed air and solvent all is good.
Replaced float needle and seats (both just to have new)
Replaced floats (all 4)
Replaced throttle cable and synced as good as can be.
Inspected Squish (its high at 0.069inch) New heads on order from vintageperformanceproducts
Inspected crank phasing it is with in .5 of a deg.
Inspected piston intake port holes (they look the same from the reed area) Wossner's there's still black coating on the skirts.
Pulled baffles (had to braze in new perforated tubes as on busted.)
Ran SS boiler brush down the stinger with baffles out (old DG pipes) scrapped all carbon out.
Leak test 20 times with water, propane, and wd40
I have run it and put a flame to gear box vent hose no change in flame so not leaking in to gearbox.
I've pointed a flame at the pipe outlet left with burn a 3 inch cone and flame will roll back in to the pipe. the right side has small change in flame brightness.
I'm waiting on new Mikuni Needle Jet Genuine 159-P0 and Genuine Mikuni Size Jet Needle 6F9 to come in.

Both my Nephew and I are running the bike this year.  His Dad built it in 84, another brother ran it 7-8 years and I joined him then stopped for a bit. 3 out of the 4 boys in my family have been lic to race on the bike and now one Nephew too.
I must figure this out.

Plug is wet firing but wet.
What have I missed?  >:(

Thanks for the help.
44
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Skill centre / Olive drab plating help!
« Last post by DrChris on June 06, 2023, 11:07:30 PM »
I would really like to get my rd400 case screws, carb clamps and a few other things plated in olive drab. My plater does a great job but the green is too light. I’ve called around and can’t find anyone here to do it. I’m game to try it myself if I have a plan or would send them away. I’m in the US.
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Aircooled RD Tech Help 250cc and Above / Re: Wet Plugs and Piston Condition
« Last post by Whitey on June 06, 2023, 10:11:41 PM »
Quote from: [Arrow] on June 06, 2023, 06:19:04 PM
18/23 x 55 = 43.04 (250LC)
21/23 x 55 = 50.22 (400C/D)
22/21 x 40 = 41.90 (OP's set up)

21/23 x 40 = 36.52 (400E/F)
18/23 x 40 = 31.30 (350LC)
21/23 x 32 = 29.21 (350A)

When I said less oil I meant on std gearing.



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That’s awesome!!… what does it mean!
I’d love to know what the numbers relate to - anyone care to enlighten me? 


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Aircooled RD Tech Help 250cc and Above / Re: 400c flasher relay
« Last post by Gr8uncleal on June 06, 2023, 09:40:08 PM »
First up, do you want to keep the self cancelling function? If yes, you'll likely need a genuine Yamaha one, and I found the later XS ones worked well. If no, then any 12v one should work, as long as your bulbs' wattage are a reasonably close match to what is shown on the side of the flasher relay (old style) or, as Rdsmoke said, a modern two pin one should work with any wattage bulbs. Obviously you'll need to consider how to mount the replacement relay.
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Restorations Diary / Re: New resto - 79 RD400 Daytona Special
« Last post by Hammer 663s on June 06, 2023, 09:33:12 PM »
Top end on, should install motor into the frame this week.

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Aircooled RD Tech Help 250cc and Above / Re: Wet Plugs and Piston Condition
« Last post by c50 on June 06, 2023, 09:00:22 PM »
Quote from: [Arrow] on June 06, 2023, 06:19:04 PM
18/23 x 55 = 43.04 (250LC)
21/23 x 55 = 50.22 (400C/D)
22/21 x 40 = 41.90 (OP's set up)

21/23 x 40 = 36.52 (400E/F)
18/23 x 40 = 31.30 (350LC)
21/23 x 32 = 29.21 (350A)

When I said less oil I meant on std gearing.



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So its less oil on 250LC's. You cannot compare LC's they are a different technology. They are leaner and hotter in the combustion chamber, higher revving and equally importantly around 20% more powerful, they need more oil as they burn it off fairly efficiently  at a significantly higher rate. They hardly smoke if they are healthy, that is because they are burning the excess oil off at higher temperatures, something the air cooled struggles to do unless really pushed, allowing it to build up if too much is going in. The balancing act with a two stroke is to get enough oil in to lubricate everything but at the same time not too much that it accumulates in the crankcases, around the pistons and in the exhaust on an average riding cycle. The important thing is to minimise any accumulations , you don't want that because it is bad for the engine and the environment. Any more oil than it takes to apply a light coating is excess that has to be burned or thrown out of the exhaust, reducing combustion efficiency and increasing emissions dramatically.  A lot of outboards that characteristically run very cool, so the oil doesn't burn off as easily, but are highly tuned, use 100:1 pre mix!

I personally would have stuck with 350B level of oiling around 50 revs per stroke and not a drop more, that is what the engine is, not anywhere near a 400F which is a bigger engine with  more power and almost certainly over oiled to try and make the cranks and bores last longer, it didn't work, they chewed up cranks and bores with as much apatite as any 400. Yet the 250 and 350's A or B's bores and cranks were never a real problem with a decent considerate owner. We used to do 12k+ per annum on them with very few issues whatsoever.
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Aircooled RD Tech Help 250cc and Above / Re: 400c flasher relay
« Last post by Rdsmoke on June 06, 2023, 07:08:41 PM »
Guys on ebay brought a two pin unit works  fine on my lc

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Aircooled RD Tech Help 250cc and Above / Re: Wet Plugs and Piston Condition
« Last post by [Arrow] on June 06, 2023, 06:19:04 PM »
18/23 x 55 = 43.04 (250LC)
21/23 x 55 = 50.22 (400C/D)
22/21 x 40 = 41.90 (OP's set up)

21/23 x 40 = 36.52 (400E/F)
18/23 x 40 = 31.30 (350LC)
21/23 x 32 = 29.21 (350A)

When I said less oil I meant on std gearing.



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Aircooled RD Tech Help 250cc and Above / Re: Wet Plugs and Piston Condition
« Last post by c50 on June 06, 2023, 05:07:42 PM »
Quote from: [Arrow] on June 06, 2023, 04:59:02 PM
Surfice to say, there is actually less oil going through that motor than a 250LC. Best ask the Yamaha engineers what they were doing there.

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Have you got the all the ratios for the lc to compare ? The 250E oil with the same porting as an LC oils only 2/3 as much as the ops set up. But you’re right leave the lubrication to the Yamaha  engineers who’s reasoning you or I have not got a clue about and no point pretending we do.
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Aircooled RD Tech Help 250cc and Above / Re: Wet Plugs and Piston Condition
« Last post by [Arrow] on June 06, 2023, 04:59:02 PM »
Surfice to say, there is actually less oil going through that motor than a 250LC. Best ask the Yamaha engineers what they were doing there.

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