Need options to try, exaust leak??

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Jpvegas333

Jpvegas333

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Sep 21, 2017
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hello. I'm a newbie to Nortons. I inherited a 1974 850 and it's been a learning process! It stalled on the freeway and when I tried to kick it over there was a air sound coming from top of motor or carb. I got it to run with full chock but it was idling very high dangerously high revs. So when I turned the choke down it stalls and lots of sputtering Only one cylinder is firing and I can feel air coming from somewhere. I've got a compression test of 90 from both cylinders with closed throttle. I'm at a loss and could use some help. Thanks
 
Jpvegas333 said:
hello. I'm a newbie to Nortons. I inherited a 1974 850 and it's been a learning process! It stalled on the freeway and when I tried to kick it over there was a air sound coming from top of motor or carb. I got it to run with full chock but it was idling very high dangerously high revs. So when I turned the choke down it stalls and lots of sputtering Only one cylinder is firing and I can feel air coming from somewhere. I've got a compression test of 90 from both cylinders with closed throttle. I'm at a loss and could use some help. Thanks
Click to expand...


It sounds like you may have a single carb manifold with one of the two center bolts that has fallen out, into the manifold. They must be installed with locktite. Jim
 
comnoz said:
It sounds like you may have a single carb manifold with one of the two center bolts that has fallen out, into the manifold. They must be installed with locktite. Jim
Click to expand...

It's got a single sudko mikuni carb. that's cool how u know that. Where are the center bolts? I'll check that when I get off work thanks!
 
if you 'feel air coming from somewhere,' you should be able to pinpoint the location, whereabouts is it now?

any more on the exhaust leak??

any info on last tune-up?

i'm guessing everything was good before just quitting suddenly? then did as u described?
 
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Jpvegas333 said:
It's got a single sudko mikuni carb. that's cool how u know that. Where are the center bolts? I'll check that when I get off work thanks!
Click to expand...

Pull the carb off and look down the hole. There are two allen head bolts inside the manifold. One of them is probably rattling around on top of the valve. Jim
 
84ok said:
if you 'feel air coming from somewhere,' you should be able to pinpoint the location, whereabouts is it now?

any more on the exhaust leak??

any info on last tune-up?

i'm guessing everything was good before just quitting suddenly? then did as u described?
Click to expand...
I couldn't tell where it's coming from. My dad adjusted valves in January Yea it was fine before the freeway. So I'll try the suggestion this afternoon. I appreciate it guys
 
comnoz said:
Pull the carb off and look down the hole. There are two allen head bolts inside the manifold. One of them is probably rattling around on top of the valve. Jim
Click to expand...

dunno about the norton, but i've seen a bolt/nut or fastener part that got loose, ending up stuck between the valve & seat,

op also said runing on 1 cyl
 
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comnoz said:
Pull the carb off and look down the hole. There are two allen head bolts inside the manifold. One of them is probably rattling around on top of the valve. Jim
Click to expand...
YEP! There was an Allen screw sitting right on top !
 
Great. Put it back in with some locktite, and pull the other one out and locktite it also. Jim
 
Well caught sir, and Jim I take my hat off to you for such a quick diagnosis,
Hopefully no damage done
On the Norton atlas manifold they had slot head screws that were staked at the ends of the screw slots,
You could if you wanted change the manifold to the two bolt type then this can never happen again
There are no issues whatsoever using just two bolts
 
84ok said:
dunno about the norton, but i've seen a bolt/nut or fastener part that got loose, ending up stuck between the valve & seat,
Click to expand...
Yup, Nortons can suffer from that too.
Took 3 of us quite a while to work it out on the side of the road on a friends bike a year or so ago.
 
I'm checking mine today :)
Had bike running well after installing some manifold/carb phenolics on all sides and losing the rubber o ring seal. Used Permatex grey between carb and phenolic and Hylomar on manifold side of phenolic

After a couple of weeks, idle started getting erratic, starts got harder...so thought idle circuit jammed up. A few attempts at #78 drill in air screw plus loads of carb cleaner sprayed in there...saw drops appearing mani side of phenolic. Snugged up carb nuts...were on low torque side...that immediately improved running and starts....but I want to go further and put the sealer both sides of phenolics and Locktite those mani bolts.
 
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