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Too much compression


elgoyoloco

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Yup choke tube is in, slides are correct and float levels are good. I definitely agree with an air leak, but its not in the engine, has to be in the carbs. I unscrewed the choke valve and pulled it out of the carb. Its was pretty caked with sand and crud, kinda makes me think it was pulling air through there. Guess I'll clean it and put it all back together then spray with carb cleaner while running to see if anything changes. I think I'll scrap the carbs anyways, they've worked hard and good  for a while, but now they're just wasting my money. Plus I'm sick of looking at them.

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Definitely not a crank seal because leak test shows good. I'm using a cooling system pressure tester for leak down so there is no bleed port. Also confirmed by immediate pressure drop when spark plugs are loosened. I'm using the single layer steel head gasket more of just a shim to drop the compression down slightly so I feel better with the readings. I'm also thinking my Snap-On compression tester is a bit inaccurate (showing high) so I'm going to borrow a coworkers to compare. Gasket flattens smoothly with adequate clamping force which shouldn't cause any etching issues. Can't be plugged main because I've been richening the mains to get the left cylinder not so lean. I appreciate everyone's help but there's really nothing left but the carbs. I'm going to dissect them some more but there's really not much to them. They are showing they're age, slide coatings are pretty much worn off and that choke valve has got me uneasy.

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Have to checked to see if the needles are in the same position? Air screws clean and same spot? Reeds in good shape?

 

I wouldn't run a gasket and a cool head... If you wanna loosen squish up and lower compression get a thicker base gasket or have domes cut... I would deff gut the carbs and look them over real close... Could be sucking the bowls dry also... Make sure vent on tank is clear and working also there's a screen on the petcock... Check to see if its clean...

 

With it passing leak down I would say you have a fuel delivery issue...

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Went over the carbs some more. Tested choke circuit on left carb with a vacuum pump and confirmed significant air leak though choke valve shaft. I'm going to remove head gasket, reset my timing to +4 and replace carbs. So the next concern is 21cc dome okay for pump gas and 28 vs 33mm pwks. I know the 33's would be too big for stock bore/stroke but would they be better for future upgrades? It's not going to be set up for drags, it is a dune machine so its going to end up with a 4mm stroker and ported to match. Most likely stick with standard bore... maybe 68's. 

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