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CB750 Barn find project - First Timer
Underdog1:
--- Quote from: Rob62 on August 26, 2018, 02:55:02 PM ---Check compression! Burned or leaky valves could be an issue.... build up of carbon on the stems can cause the valves to stay open once warmed up (i had this issue back in the 80’s)... a re-lap of the valve seats transformed the motor. A compression test will help, when cold and also at running temp... keep going, you will get there.
--- End quote ---
Ok sounds easy enough, lapped all the valves and cleaned hem up during the rebuild but I’ll recheck clearances and do a compression test this week.. just need a compression gauge.
Are the cheap ones that come in a red plastic case (all over amazon and eBay) for about £12 good enough?
Nurse Julie:
10-15 minutes riding sounds quite a long time for something fuel or electrical related to show itself. Could it be the top end of the engine getting very hot for some reason and partially seizing due to metal expansion? Cools down, contracts and off you go again. My theory is based on nothing more than Women's logic here 😁😁
Underdog1:
--- Quote from: Nurse Julie on August 26, 2018, 03:10:11 PM ---10-15 minutes riding sounds quite a long time for something fuel or electrical related to show itself. Could it be the top end of the engine getting very hot for some reason and partially seizing due to metal expansion? Cools down, contracts and off you go again. My theory is based on nothing more than Women's logic here 😁😁
--- End quote ---
I had something that felt similar on a hornet I had, would conk out after 15 mins and not restart until it cooled down, was a burnt connector from the stator and a duff rectifier causing the battery to not charge.
I get 14.5v over the battery with bike on or off which seems fine. Would be good to rest when the battery is depleted a bit I suppose to make sure the voltage jumps up when it starts
Bryanj:
The 12 quid ones are crap mate
Underdog1:
--- Quote from: Bryanj on August 26, 2018, 03:22:57 PM ---The 12 quid ones are crap mate
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Maybe I’ll stretch to the £18 ones then :D
Not had time to work on the bike today but quickly whipped the carb bowls off and fuel flows fine, embarrassingly I thought the off and reserve settings on the pet cock were the other way round so half the time I was probably trying to start the bike in the off position!
Now it’s even possible that I ran out of fuel on the on position as I put a Jerry cans worth of fuel in then continued to try and start the bike in the off position and I did fanny about with the peacock a fair bit during breakdowns, perhaps I filled the carb bowls up when I though it was switched off and then drove a mile or so with it actually switched off thinking I was on reserve until the bowls emptied again..
Anyway I can’t see any sparks at all at the points one of the spark plugs seemed loose and this is the colour they’re at
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