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Aircooled RD Tech Help 250cc and Above / Re: Master cylinder
« Last post by chrisg.007 on September 24, 2020, 07:44:49 PM »
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Aircooled RD Tech Help 200cc and Below / Re: RD200DX speedo and tacho needles
« Last post by pidjones on September 24, 2020, 06:05:38 PM »
I have also used Tamiya paint on needles. But, it wasn't a Yamaha,and I wasn't trying for matching of the original - just  making it very visible. I used a Day Glow Orange on a replacement needle that I made (Old one shattered on the shake-down run. I swear I wasn't going that fast!) for a CB750F. The pant and needle worked great.
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Aircooled RD Tech Help 250cc and Above / Re: Yamaha RD350, Type 351 Engine probs
« Last post by Ironhead on September 24, 2020, 06:02:00 PM »
When choke assembly of left carb are is done i will time the engine with a dial gauge to 2mm BTDC.

Thanks for your help !
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Aircooled RD Tech Help 250cc and Above / Re: 77 rd400d trouble - need help
« Last post by Salman_z8 on September 24, 2020, 06:01:01 PM »
Pretty neat setup.
Since i have some shaky faith with the chinese ignition, i have sourced some used points parts to test. So back to points and see if it shows signs of improvement. Take the carbs off again and fix the tach drive leak.
I will do the leak tests over the next few months and need be then just pull the motor.

Have too many other projects, and i hope it doesnt need the seals just yet, otherwise it would have to wait for a while.


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Aircooled RD Tech Help 250cc and Above / Re: Crank seal orientation e/f rd250
« Last post by Astute Greaser on September 24, 2020, 05:40:57 PM »
+1
Look at the U shape at the bottom of the seal. When pressure is applied this will expand the lips against the inner and outer wall faces of the forks creating the seal  ;) Doesn't happen with seal other way round.
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He may be ill  ???
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Aircooled RD Tech Help 200cc and Below / Re: RD200DX speedo and tacho needles
« Last post by Barnett on September 24, 2020, 05:20:26 PM »
On kawasaki meters I have used tamia (spelling?) model makers acrylic paints on needle tips with good results and no fading. If you go to a craft shop or model makers shop, i.e. aircraft, cars, bikes etc you can have a look at the vast range available.
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Aircooled RD Tech Help 250cc and Above / Re: Yamaha RD350, Type 351 Engine probs
« Last post by Barnett on September 24, 2020, 05:01:35 PM »
Hi

Be best to check the timing with a dial gauge to 2mm BTDC, set your points to 0.3 - 0.35 max beforehand. needle should be in 4th position.

The exhausts look ok, they are not restricted are they? Also were the down pipes considerably longer on some bikes in Germany, maybe 250, might have got swapped if so?  There are new exhausts available from csmnl, quite reasonable price too! I am not sure but suspect they might be pattern? Yours looks quite new, rather than re chromed, could they be these pipes?  Have a look on cmsnl.   (   https://www.cmsnl.com/yamaha-rd250-1974-rd0-europe-24rd0-300e1_model38123/partslist/0013.html#.X2x2BzrPyUk ) It does sound like a resonance effect.

Other stuff to check is wear in the carbs, slides, needles and needle jets. Not common unless the bike has done many klm's, so not too common ! Make sure the choke is sealing off well. Float height, 14-15mm? And the Air correction intake jets in the bell mouth are clear through to the needle jet enclosure.

+1 you MUST use a dti to set timing, strobe on aprox timing mark is no good and only an approximation although I don't think ignition timing is the problem here.
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Aircooled RD Tech Help 200cc and Below / Re: 1.5mm btdc
« Last post by Mountainsofbeer on September 24, 2020, 04:45:27 PM »
I'm in the US  and its a really small movement, less than 1/16th of an inch if I remember I had to convert it just to get a reference. And its always near where the engine wants to rotate on its own  which makes it harder for me to check lol.

Usually my points wear advanced and I can tell by less torque and the powerband comes on with more pulsing I guess but that could be because I had one side worse..warm idle sounded alittle off too.

So again it is just a tiny movement downwards for the piston, if your turning it more than that you might be off by alot
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Aircooled RD Tech Help 250cc and Above / Re: Yamaha RD350, Type 351 Engine probs
« Last post by Ironhead on September 24, 2020, 04:38:38 PM »
Thanks c50 for the hints.
Today disassembled both carbs again. Found air leak in choke assembly.
O-ring totally distorted.
This would explain that left cyl. runs leaner and gets hotter then right pot.

Ordered a lot of spare parts for VM28-SC from Topham Mikuni Germany.
Did a compression check kicking engine cold. Result both cyl. 7 Bar
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