I’ve lost patience with the poor starting of the inter and seek to eliminate different elements. I have a 930 concentric but it’s not jetted anything like the TT. Can anyone running this set up give me a starting point on jets? The tt is 109 / 320 with No 7 cutaway.
The 930 max slide is 5 cutaway but that should not affect starts. Replaceable pilot jet also so that’s a newly for me. if I can have a base set up from one of you I can then get running and bedded down.
Many thanks
Jon
I have no..
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Pilot jet 17 matches the…
Pilot jet 17 matches the default 4 stroke pre premium pilot bush 25 but this does show up as lean on 850 and some 750 twins, so a pilot jet 19 may be better than a pilot jet 17. If you get best tickover at under 1 turn out with a 17 then try the 19 to bring it out to the correct range of 1 to 2 turns out. Starting point for pilot mixture screw is 1.5 turns out and it controls the air not the fuel.
http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html
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Thanks John & Ian
The 930 I have is pretty much set up as you suggest, with the exception of the pilot jet, that is vacant, (ordered at Burlen).
So a bit of cable work and fit the ES2 stand to stabilise it for now. Will be next weekends exercise.
Thanks again
Jon
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Inter Concentric
I have had a 930 concentric on my ‘37 500 Inter engined post war plunger Manx since it was put back on the road in 2009. Worked perfectly out of the box from Surrey Cycles with the following settings
310 mains, n/jet 106, pilot 30(bush removed)
slide 3
Helps if you have a good mag, starting is then normally 1 or 2 kick affair with a steady tick over
hope this helps
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Thanks Simon
That's perfect. Do you know why they reverted to pilot jet and bush out? Mag has been redone and engine rebuilt with new rings, valves and guides. Up until last year I had been run and bump starting, but I'm passed that now. Have modified the gearbox to take a kickstart. As I said previously its a Manx Spec engine so there is no decompress.
Will get on with making cable up this week and see how I go next weekend.
Thanks again
Jon
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The bush was in the…
The bush was in the preferred 4 stoke position but always a 25, so if you needed a 30 you drilled out the 25 pilot bush well oversize or pushed it out so it was no longer an influence, Then you screwed the 30 pilot jet into the pre drilled position for 2 stroke pilot jets. The premier 19 pilot is the same size as the old 30 pilot jet.
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Ok, it now runs....
First job was fit a centre stand. Stripped off the TT carb and cables, bought a refurb kit for the 930 concentric and made up new cables to suit. . Bolts changed for studs to hold the carb on as the tickler is in the way for a bolt. Fuel lines changed for push on type. So now the carb is not in question.
Checked ignition gaps and timing; quick check on valve timing to confirm set up, fresh fuel and boots on.
A few kicks and a kick back and she was away. I warmed and settled the motor down and decided to check the ignition timing with a strobe .As recommended I set it at 37 degrees on a fag paper at full advance. But my strobe was telling me 48 Degrees. With the flat advance lever giving more than 50 degrees of variation I have now retimed to give full advance of 40 degrees and retard at 5 degrees by slackening the cable.
Now she starts , ticks over and revs out cleanly. Road tests for my Xmas holiday as long as weather permits.
Now to find out what’s not right with the TT.
cheers all
Jon
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.. specific info but I'd start rich and work my way down. The main jet is only used at WOT so I'd go big there to make sure it doesn't restrict flow to the others - you can sort it out when you get it running and starting properly. Needle jet 106, needle in central position, 3.5 cutaway should be a decent starting point.