Author Topic: T35 Engine Mods?  (Read 5442 times)

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Offline aggettd

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T35 Engine Mods?
« on: 16 Jun 2005 at 01:53 »
Would anyone be able to suggest where I might be able to get comprehensive information on modifying the T35 engine for reliability, specifically?:

1. timing end crank roller bearing conversion
2. preventing crank from spontaneous pretzelization

For those interested, the crank from my '47 T35 is now in the shop for the third time, being straightened. The last time it was straightened I had the outer ends of the pins TIG'ed. Now I get the inner ends welded. Disassembly when I next have to change the big-end bearing should be interesting. There has got to be an alternative. Any suggestions??

Anything else I should be modifying while I have it apart? By the way, I'm now down to 1 hour 50 minutes to remove the engine and disassemble motor to the point where the crankshaft is free in my hand. Unfortunately, reassembly and installation of motor is still around 4 hours.

David Aggett
Nova Scotia
Canada

Offline Doug

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T35 Engine Mods?
« Reply #1 on: 16 Jun 2005 at 03:03 »
David,

The postwar lower ends do not like to be pressed apart and together repeatedly, as I think you have discovered.  The holes stretch.  This is why the factory used 0.004" oversize crankpins on refurbished shafts; so they could re-hone the holes true.  

George Easton raced a modified postwar Mark with needle bearing conversion.  You will probably find insufficient material to inset a roller bearing.  Might need a hard sleeve put on the crank.  You have to convert to quill oil feed to the end of the crank; not a bad idea in any event.  Seem to recall it was written up in an old NCR issue.  

As for keeping the crankshaft from twisting, the press fits have to be just right, or you do a bodge like tack welding (and you are not the first to resort to that.)  The Easton racer with special cylinders was well over 350cc, and had a full disk center web, but still relied on the press fit pins, so far as I know.  

-Doug

Offline trevorp

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t35 mods
« Reply #2 on: 17 Jun 2005 at 08:27 »
sounds like real problems with crank i may have one but may be in worse nick than yours i will have a look on the weekend and let u know
i am having problems working out the corresct gap for everything
i have t35 mk1 and stamped on crankase is set tappets at 10 thou in the manual it says 2 thou inlet 4 thou exhaust
and point gap which i had presumed at 12 to 15 thou the book says 4 not to mention adjusting the timing in full retard and not advanced as i have been told
ah douglases there seems to be heaps of missinformation on these bikes
maybe this may have some relevance to your crank bending
what do u set your bike up to spec wise

Offline aggettd

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T35 Engine Mods?
« Reply #3 on: 18 Jun 2005 at 16:40 »
I set the tappets at the recommended 2 thou. My manual says 2 thou. cold or 4 thou. hot for both inlet and exhaust. Seems awfully close, but the gap impacts valve timing as the bike seems to start easier with the close gaps.

I set the timing static on full advance with a degree wheel attached to the crank by a pair of puck magnets. I use 40 degrees BTC (or as close as I can get it, the spec is 43 degrees) for full advance ignition timing, using a strip of cigarette paper in the points as a tension feeler (I set the timing just as the paper begins to pull out with a gentle tension). Note that the 4 thou. point gap is to be measured at TDC, not maximum. I find it easier to use 12 thou. at maximum opening instead, because it's easier to find max opening for routine tuneups rather than fiddling around with trying to find TDC. They work out pretty close anyway.

When I got the bike, it had been set up according to Mk 3 specs, and was difficult to start. Now, on those rare occasions that the crank is not twisted, it starts in the first three kicks, often first or second.

I have been looking for a crank to set up correctly (not with a temporary bodge, as Doug so accurately suggested), so if there is one available, I'd love to see pics and determine if it is serviceable. Right now our riding season is rapidly passing, so I am just keen to get back on the road, even if it means welding my old crank as a temporary fix.

Offline trevorp

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t 35
« Reply #4 on: 19 Jun 2005 at 13:25 »
i have just been out and set the tappets to 2 thou and what a difference
runs even smoother
i am coming under the view that the man who stamped numbers on douglas bikes may have had a bottle of whisky in his jacket as my t35 mk 1 has set tappets to 10 thou stamped on case near cylinder barrel
well its the last time i will start it as its in for the big refurbishment
i will send u a picture of the crank its a bit rusty but if ok u can have it just pay for postage if thats feasible im not up with postage charges

 

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