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Author Topic: 73ish Cb750 won't idle and drinks way too much fuel  (Read 2864 times)

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Offline Don R

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Re: 73ish Cb750 won't idle and drinks way too much fuel
« Reply #25 on: June 27, 2019, 08:07:15 PM »
Use the clear tube fuel level check method. That will tell you how the floats and float valves are working.
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Offline OperatorAndy

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Re: 73ish Cb750 won't idle and drinks way too much fuel
« Reply #26 on: June 30, 2019, 07:13:40 AM »
Clear tube method is a good idea. I'll do that today. A friend Stopped by yesterday and we redid a few checks. Because it's idling better, we were able to run it longer. That fuel that I'm going through... it's going into the oil for sure. So we checked compression again. This was the first time checking after I closed the valve gaps to spec. Just over 100 on all four. Seems low. I was getting 140 to 150 when the valves were closing too early which makes sense.  But now I feel like 100 is too low. Thoughts? BTW. .. a lot of fuel is getting into the oil. Can't run her like that!
« Last Edit: July 01, 2019, 06:53:33 PM by OperatorAndy »
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Offline OperatorAndy

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Re: 73ish Cb750 won't idle and drinks way too much fuel
« Reply #27 on: July 01, 2019, 07:06:00 PM »
Ok... drained and refilled with oil. I'll do a float check tomorrow with the clear tube. I just have an old hard clear tube that I threaded to fit in the drain hole. It works without leaking. What do others use? I forget the thread on there but I know I didn't have any screws or bolts that fit (other than the drain screws). I know that there’s a product, but diy stuff? Could the “fuel in oil” be valve related? I don’t think I have a head gasket issue as I just installed all new gaskets and valve seals and was very careful when cleaning and reassembling the engine. I have done this before on other engines without issue.

I just looked up what compression others are getting and my new 100-psi results are concerning to say the least!
Oh boy… Help needed!

Btw.. if anyone is looking for engine parts, I have the full internals for the engine that I salvaged the case from. I’m in Canada though, so shipping is a killer eh!
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Offline disco

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Re: 73ish Cb750 won't idle and drinks way too much fuel
« Reply #28 on: July 02, 2019, 04:21:56 AM »
You did hold the throttle wide open while doing the compression check?
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Offline OperatorAndy

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Re: 73ish Cb750 won't idle and drinks way too much fuel
« Reply #29 on: July 02, 2019, 09:19:22 AM »
Quote from: disco on July 02, 2019, 04:21:56 AM
You did hold the throttle wide open while doing the compression check?

No. I pulled all 4 plugs and moved the gauge from cylinder to cylinder.  Is there another method?
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Offline OperatorAndy

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Re: 73ish Cb750 won't idle and drinks way too much fuel
« Reply #30 on: July 02, 2019, 11:10:32 AM »
OK. .. checked compression again. About 100 at closed throttle and 145 to 150 at wot. Thanks so much for the tip. I had the carbs off when I first checked and had numbers in the 140s. The next time I checked, they were back on.
Can't use clear tube to  check floats. I may have packed the tube for the big move! Lol
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Offline OperatorAndy

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Re: 73ish Cb750 won't idle and drinks way too much fuel
« Reply #31 on: July 05, 2019, 07:33:01 PM »
Still.... how can all this gas be going into the oil when this thing is running?
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