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Post by nsman on Oct 1, 2015 12:46:05 GMT -5
After way too long I finally got my 76 KH250 back on the road. It worked only OK at first, but I sourced three KH250 carb kits that have now returned it to what I think it should be. The carbs are all jetted and set up to spec 75 mains,20 pilots and float hts all set at 25 mm, air screws all set at 1 1/4 What I do not understand is why the far left spark plug is very dark brown,the centre is light brown and the right side is medium brown.... Compression reads 120 psi for all cylinders(its a cheap ctc guage)so could be more or less but they are all the same.Starts and idles fine. I think there is some piston slap from the left hand cylinder,but disaapears when under load.The left and right pistons and rings are used(from this engine) but the centre is new old stock..they are all .50 oversize.The crank is completely rebuilt,new rod sets and bearings and seals. Hope I have given enough info for the learned
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Post by Walms on Oct 1, 2015 13:18:12 GMT -5
3 things come to mind... an air leak, bad carb sync. Or timing.
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Post by zambia on Oct 1, 2015 14:11:40 GMT -5
The carb kits are known to be inconsistent too. I'm guessing they are Keyster or such like.
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Post by nsman on Oct 1, 2015 14:30:29 GMT -5
3 things come to mind... an air leak, bad carb sync. Or timing. If there was an air leak,would the plugs(at least one) be looking lean? I synced them with a drill bit and then adjusted the idle...is there a better way? The points gaps are all .014" and the timing was adjusted and checked with a reliable timing light.
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Post by nsman on Oct 1, 2015 14:34:10 GMT -5
The carb kits are known to be inconsistent too. I'm guessing they are Keyster or such like. A keyster kit it is, Is it OK to adjust each carb differently,or am I just masking an issue? I am using resister plug caps,with that cause a problem if the coils are all in different states of output ?(they are old and original.
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Post by zambia on Oct 1, 2015 14:52:42 GMT -5
The jets in Keyster kits are worse than re-using the old brass. If you still have the old brass, give it a super cleaning and put it back in (mains, pilots and jet needles). Also, I don't think the KH250 came with resistor caps...and it has a fairly feeble ignition so I would swap those caps and wires too. On my 250 I noticed the air screws were all slightly different settings but the rest of the carb settings should really be the same
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Post by nsman on Oct 1, 2015 15:55:35 GMT -5
I have changed the wires already and really I only needed the needles and seats in the kits as they were worn and leaking so I can clean the jets and reinstall. I have used Keyster jets kits in the past with positive results.I was getting the same plug readings before the kit install,but I could not keep the carbs from flooding.I will change out the resister caps as well. Thx for your input.
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Post by zambia on Oct 1, 2015 16:20:04 GMT -5
I have changed the wires already and really I only needed the needles and seats in the kits as they were worn and leaking so I can clean the jets and reinstall. I have used Keyster jets kits in the past with positive results.I was getting the same plug readings before the kit install,but I could not keep the carbs from flooding.I will change out the resister caps as well. Thx for your input. I think that should get you on track. The other possible issue is that the pipes could be clogged - mine were full of stuff a mouse dragged in.
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Post by Walms on Oct 1, 2015 16:27:51 GMT -5
Be sure to set the idle screws so they all just touch the slide for the base line and then sync the cables. It's nice to have a syncing tool but not mandatory. But if you at least confirm idle screws are good, you can even just listen to see if slides leave home at the same time. I use the 2 finger method and my head temp gauges are close to confirm.
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