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Aircooled Mechanical Tech A Q & A Forum devoted to Aircooled Mechanical Issues. Got a problem? Then ask in here. Please, no 'For Sale' or 'Want To Buy' ads, plugs for your 'business', links to 'for sale' ads or Ebay links to your (or your mate's) auction (use the VZi 'Classifieds' section) - this also includes thinly veiled 'What's My Car Worth?' threads and "Who Can Sell Me A . . ." posts.

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Old 18-02-2019, 11:31 AM   #61
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If the piston/slide lifts too fast under excel it will create a flat spot. On an S.U... IF there is a flat spot it can be fixed it with a thicker oil in dashpot or a stronger spring. Your carb will have a spring in the top holding the piston down. Try lifting the piston there should be resistance. So see if you can find a stronger spring. If you cant find a stronger spring you could make the piston/slide heavier.

So. If the piston/slide rises to fast too much air will go into the engine creating a flat spot
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Old 18-02-2019, 03:47 PM   #62
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Quote:
Originally Posted by GARRICK.CLARK View Post
If the piston/slide lifts too fast under excel it will create a flat spot. On an S.U... IF there is a flat spot it can be fixed it with a thicker oil in dashpot or a stronger spring. Your carb will have a spring in the top holding the piston down. Try lifting the piston there should be resistance. So see if you can find a stronger spring. If you cant find a stronger spring you could make the piston/slide heavier, so long as its heavier.

So. If the piston/slide rises to fast too much air will go into the engine creating a flat spot
Brilliant, that makes sense
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Old 19-02-2019, 07:39 PM   #63
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Quote:
Originally Posted by GARRICK.CLARK View Post
If the piston/slide lifts too fast under excel it will create a flat spot. On an S.U... IF there is a flat spot it can be fixed it with a thicker oil in dashpot or a stronger spring. Your carb will have a spring in the top holding the piston down. Try lifting the piston there should be resistance. So see if you can find a stronger spring. If you cant find a stronger spring you could make the piston/slide heavier.

So. If the piston/slide rises to fast too much air will go into the engine creating a flat spot
I have had a look to see if they do a heavier spring but can't find anything. What would you suggest to use the weight the piston and how much weight woukd you recommend? Cheers
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Old 20-02-2019, 10:31 AM   #64
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Could you put a shim on one end of the spring. That would put more tension on the spring. But may also cause it to go coil bound before it should.


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Old 20-02-2019, 11:01 AM   #65
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Could you put a shim on one end of the spring. That would put more tension on the spring. But may also cause it to go coil bound before it should.


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Good idea
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Old 20-02-2019, 03:08 PM   #66
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As leigh says really. try fitting a round disc inside the piston/slider. I take it.. it's the same as the su piston were the piston is hollow and the spring slots inside it. If so fit a round steel disc into the piston to weight it down . The weight of it is a guess thing,you might have to increase it or reduce it.
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Old 28-03-2019, 03:06 PM   #67
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After a lot of messing I now have it running.

https://youtu.be/sO1uL70sTDU
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Old 28-03-2019, 06:52 PM   #68
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Is it running good.
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