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About armac

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    New Member
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  • Bike
    Triumph Tiger Cub
  • Club
    Yorkshire Classic

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  • Location
    North Yorkshire
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  1. TrialsrFun, back to you! I run a breather from the crankcase & the rocker box that goes into a one way valve, that exits into the steering head lubing the bearings & preventing any water from being sucked in. It runs a little bit cleaner on the carburation than having no breather at all. All the best, Duncan.
  2. Brucey, sorry for delay, Cub engines can certainly run hot, one of the tips from Triumph was to ride through puddles in the scottish 6 days to aid cooling. Modern synthetic oils are able to withstand much greater temperature gradients without breaking down and are infinately superior to Castrol R. You had better check with Richard Thorpe ( PJ1 importer) about swapping directly to synthetic, his email is (not sure if this is public, might be best to say I gave it to you!). The little hole in the inner case does want welding up as its original job was to suck oil up that had leaked from the camshaft & gearbox. On a trials engine that has been through streams etc , then power washed, you are inevitably sucking up water as well. Best regards, Duncan.
  3. HI, you might have sorted this already but: 1: shimming the gearbox. If you have too much play on either the mainshaft or the layshaft, this can cause false neutrals. 2: If you are running a trials top gear, the 16 tooth layshaft gear is interchangeable with the 16 tooth first gear. However, it is thinner, and if you have inadvertently got the 16 tooth layshaft gear where the first gear should be, you will have a load of play on the mainshaft. 3: If the crank case bolt that comes from the left side of the crankcase is too long, it pressurises the selector spring and prevents it changing properly. If the selector plate is badly worn, that will stop it staying in gear correctly and could give false neutral. 4: there are 2 spring loaded teeth on the selector shaft. If these are badly rounded, and/or the springs are weak, again can cause the problem. It is worth doing a general inspection of all the dogs on the gears, to be sure they are not badly rounded. Good luck! Duncan, Armac Design
  4. Hi, you may have sorted this already, but: use semi-synthetic or fully-synthetic (I use PJ1 and am still running the original big end after at least 15 years). Synthetics have a much higher temperature range and molecular breakdown is much less than mineral oil. It is more expensive, but cheaper than rebuilding the engine. I hope that helps. Duncan, Armac Design
  5. Hi Jimmy, Duncan here, Just picked up this thread. Your valve clearances sound very tight, have you got the correct clearances for your camshaft as they are different for the "R" cam & the road cam. I have tried tightening down the clearances to make the engine run a bit sweeter, but experienced a similar result to your problem. Also worth checking your push rod lengths, these do wear at the cam follower end then don't open the valves fully. I have gone over to steel ones. the original cub valve springs are incredibly variable, I no longer use them, instead I use springs from a speedway motor. I have also known cams to have been mis-machined so that the cam gear is in the wrong place so the cam timing is out. Judy's bike had a problem in that the valve spring pocket in the head had been badly machined so that it penetrated through to the inlet passage, I imagine that this could happen on either port. However as your engine seems to run sweetly at the bottom my guess is that it is electrics. The only way to sort that is borrow a set & then try one thing at a time, starting with the coil, oh check that the air gap around the rotor is correct, & that the main bearing on that side is in good condition. If it's worn then the crank bouncing up & down will bugger the air gap. the golden rule is only change one thing at a time so you can be sure it's illuminated. Hope you don't get to the stage where the one thing is the bike! see you at the 2-day. Cheers, Duncan.
  6. Hi, Alan is exactly right: you can't notice the difference with a 3mm offset. A friend of mine (a wheel builder) had been racing a 650 Triumph Twin for a number of years and discovered that the rear wheel was 10mm out of line. He rebuilt it correctly, in line, and said he couldn't notice any difference. So with wheel alignment, although in theory is best equally spaced around the centre line of the bike, small offsets in reality make little difference, especially in low-speed pre-65 trials!. Cheers, Duncan
  7. Hi Dan, Duncan Macdonald from Armac Design here. Not sure if you've solved this yet, but my advice is: all the extra effort to reposition everything is not worth the small gain you'd get by moving the engine. It is much easier and more efficient to offset the rear rim 3mm to the right which will give you the tyre clearance you need. Also you can widen the swinging arm on the right, if it hasn't already been done. Good luck!
  8. I always say, what's a dunny? and then my wife, who is a Kiwi, tells me...
  9. Hi. Duncan Macdonald, Armac Design here. Hollow aluminium spindles are fine if they're made from the correct specification of aluminium, but you can only have a hollow spindle if the outside diameter is large enough to withstand having a hole through the middle of it. Our spindles are not hollow, because the diameter is not large enough (16mm dia); pre65 bikes generally have smaller diameter spindles than modern bikes. If you are using cast iron hubs, there's little point putting an alu spindle through because the weight saving, relatively, is minimal. Best to target the big stuff for weight saving first! cheers, Duncan
  10. It's virtually impossible to get stuff from Serco since Martyn Adams sold it. If you want pre-65 parts the best bet is UPB Bikes. Website is, tel 01977 642275, main man is Bob Moore. They have good stock levels and efficient service. Direct link