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Opinions needed please...

  • Thread starter Thread starter TheCafeKid
  • Start date Start date
T

TheCafeKid

Guest
On my 77 750 i have a couple of issues i need opinons on. I'm pretty good with motors, and i have a pretty good idea of whats going on, though four banger's carbs still give me a bit of fits with the syncing.. but before i start tearing into it while the weather is still nice enough to ride, i wanted to what you guys think.

First: Recently i noticed that im blowing a bit of gray smoke thru the exaust on downshift and at sitting revs. Upon further inspection i also notice it's blowing a little bit out around one cylinder's manifold gasket. Assuming i have a leak there, which is no big deal to fix, but when i pulled the plug on that cylinder i have found its a bit black and wet with gas. I am guessing that cylinder is running a bit rich, which is where my grey smoke is coming from. Now this bike (up untill today, see next issue) ran and idles pretty darn good. I also think one of the cylinders (the one right next to it i am not sure how they're numbered but if on the bike left to right these two cylinders would be 3 and 4) it blueing a bit on my header, which seems to indicate a lean mix in that cylinder Right??

Issue #2

Today i have noticed an intermitant fairly audiable (at least at idle) ticking. It's hard to pinpoint where exactly its coming from, but it sounds as if its coming the frontside cam. I added a bit of oil and it didnt go away. I would normally think this would be a valve lash or cam chain adjustment? but its intermitant, wouldnt a cam be pretty regular? and which?? lash or chain? This is my first DOHC so im still learning a bit The bike runs pretty damn smooth so i am also torn as to whether to break it down now to avoid damage or wait till it's near time to park her for the winter...

what do you guys think?? Thanks for the input in advance!!

TCK
 
First thing, adjust the valves. You will need a $15 tool to depress the valve buckets to remove the shims...and of course, some new shims.

After you get this done, do a compression test - with engine warm and throttle wide open. Could be your smoke is from burning oil. A compression check should tell the story.

Good luck.
 
Thanks for the input. I used to live in Torrance :) Anyway... At first i was thinking oil too.. but there's no blue tinge to the smoke, just grey, and its not heavy like buring oil smoke so i think it to be unburned gas. Ima change out the plugs and wires too, they are a bit old. And upon further review of the ticking noise, (im one of those people that will obsess about a knock or ping or squeak coming from a vehicle...its a curse and it makes me crazy) I actually stuck my head all around the running motor and it actually now sounds like the tick is coming from bellow the cams, like a bad firing in a cylinder. The tick now seems to coincide with a deadspot in vibrations which i can feel thru the bars...cant hear it in the idle tho..weird... I still could be wrong, and a valve adjustment is going to happen anyway, but im starting to think i have bad fire....more opinions please!!

Thanks all!!

TCK
 
TheCafeKid said:
(im one of those people that will obsess about a knock or ping or squeak coming from a vehicle...its a curse and it makes me crazy)
Click to expand...

... then you might have the wrong brand of bike! I'm not sure about the 750, but in its later years, my first 850 sounded like the soundtrack of Metropolis.

Definitely look over the lash, followed with a compression test. Primarily, though, I'd suggest just enjoying the bike for a while. Put a few thousand miles on it, and see how things go.
 
Ticking is a very common sound from these engines. I have often thought mine sounds like a team of crickets chirping while their friends and other team members perform tap dances in a tin can.


If you really want to isolate the sounds, try using a mechanic's stethoscope, or if none is available, a wood handle from a broom or mop. (Handle only, please....Hallowe'en is still a month away):)
 
Thanks guys!! I really appreciate the input! I just want to make sure that putting the valve adjustment off till winter when i can break the whole thing down (it needs gaskets too. got little leaks here and there but no puddles under it so thats good hehe) wasnt going to do serious damage. I have been told that these old 8 valvers are pratically bullet proof, so i really hope so. Picked up new NGK's today, ill install those and see if she runs a bit better, plus i'll gap the 3 cylinder (the one that smokes) to the full .028 and see if a longer spark gets rid of my smoking prob. Doan think it will but ya never know. There's a hi po shop down the road and i may have them look at the mix on the carbs too.. And this winter she'll get the full massage treatment...maybe ill have to learn to love the noises...hehehe
 
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