Order of Operations?

[ZoSo750]

I've got my 82 750T running finally, not perfect, but not terrible. So now I'm on to something I've been contemplating for a week or so. I sync'd the carbs but I've still got a low-end "stumble" and at when cruising the motor kind of bogs and slows down unless I'm sending fuel to the carbs. That being said, I want to do plug chops but I've got some wild valve noise and I haven't even popped the valve covers to see what everything looks like and I know they haven't been adjusted, much less looked at, in at least 5 years.

Would adjusting valves before doing my plug chops be a better idea than doing the chops first?

 

[tom203]

Unfortunately, adjusting the valves should have come before the carb sync'd, since they have alot to do with intake manifold pressures.
What does "unless I'm sending fuel to the carbs" mean exactly?

 

[ZoSo750]

Really? I thought that sync'ing was mainly to do with air/fuel ratio via having each butterfly open and close at the same and at the same rate, not manifold pressures... Crap! :-s

"On the throttle" is what I meant by that. Sorry, I'm a diesel tech, so I don't typically use that word

 

[blowerbike]

I've got my 82 750T running finally, not perfect, but not terrible. So now I'm on to something I've been contemplating for a week or so. I sync'd the carbs but I've still got a low-end "stumble" and at when cruising the motor kind of bogs and slows down unless I'm sending fuel to the carbs. That being said, I want to do plug chops but I've got some wild valve noise and I haven't even popped the valve covers to see what everything looks like and I know they haven't been adjusted, much less looked at, in at least 5 years.

Would adjusting valves before doing my plug chops be a better idea than doing the chops first?

careful with those wild valve noises...
i have had more than one 80-82 750 brought to me for valve adjustments only to find out that the engine had spun a rod bearing.
the noise is that light..
the sounds comes from the piston hitting the cylinder head, when you rev it up it gets louder and more consistent.
good luck.

 

[apogeecustom]

Really? I thought that sync'ing was mainly to do with air/fuel ratio via having each butterfly open and close at the same and at the same rate, not manifold pressures... Crap! :-s

"On the throttle" is what I meant by that. Sorry, I'm a diesel tech, so I don't typically use that word

It does have to do with how much mixed fuel is leaving the carb body. The valve on the other hand has a relationship of time open/closed and passage volume. If this is out of spec you have a new problem of too much or not enough material, i.e. mixture or gases left in the chamber which is now a pressure issue on the next compress cycle of the piston.

 

[tom203]

Diesel tech! what size do you typically work on?
Sorry about "intake manifold pressure" wording I used- I'm sure it sounded confusing to someone who works on multi cylinder engines sharing a common intake.
Anyways, airflow thru carb throat depends on piston creating a decent and consistent vacuum on its intake stroke. Leaking valves would interfere with this is what I should have said.

 

[ZoSo750]

Diesel tech! what size do you typically work on?

I work on Powerstrokes for the most part. A Cummins every now and then.

I got a lot of work ahead of me it looks... The sound is consistant and does not change with engine RPM. I'm tearing the motor down once it gets too cold to ride but I hope adjusting the valves will fix it! Thanks for the input!

 

[Big T]

I got a lot of work ahead of me it looks... The sound is consistant and does not change with engine RPM. I'm tearing the motor down once it gets too cold to ride but I hope adjusting the valves will fix it! Thanks for the input!

You should isolate where the sound is coming from with a stethoscope

Valve and camchain noise should increase with rpm

Why would you tear the motor down?

Is it low on compression?

 

[ZoSo750]

You should isolate where the sound is coming from with a stethoscope

Valve and camchain noise should increase with rpm

Why would you tear the motor down?

Is it low on compression?

The only reason I'd tear it down is just because that's how I am. I enjoy that kind of stuff and that way I know that everything inside has been overhauled or replaced if necessary. Just peace of mind is all . The noise also may get louder with rpm, but the pipe that's on there makes it a little difficult to hear anything other than exhaust haha.

I took the valve cover off last night though and went to align the marks on the camshafts and noticed that they don't line up as if the chain jumped a tooth on the sprocket? I haven't looked into it much beyond that, but would a bad chain tensioner allow this to happen? There wasn't much backlash on the chain when I wiggled it.

 

[tom203]

I took the valve cover off last night though and went to align the marks on the camshafts and noticed that they don't line up as if the chain jumped a tooth on the sprocket? I haven't looked into it much beyond that, but would a bad chain tensioner allow this to happen? There wasn't much backlash on the chain when I wiggled it.

Go to electrical forum and look for post by drycell- in the replies there's a good pic of the timing marks on the crankshaft. Understand how the marks here and the camshafts positions are determined before you assume anything. Yes, it's possible it jumped a tooth but be very careful. The cam tensioner could have been installed wrong or stuck at one time.

 

[81GS750]

I work on Powerstrokes for the most part. A Cummins every now and then.

I bet those Powerstrokes keep you pretty busy!
It took a bit of turning before the marks lined up on my 750. I would think you would see evidence of the chain jumping a tooth on either the chain or one of the cam gears.

 

[ZoSo750]

I bet those Powerstrokes keep you pretty busy!
It took a bit of turning before the marks lined up on my 750. I would think you would see evidence of the chain jumping a tooth on either the chain or one of the cam gears.

Hey! I drive a 7.3L and I don't have problems! It's the 6.0L's that pay the bills anyway

As it turns out though, everything was fine and the marks on the right side ends of the cams did line up after all. Must've been a little darker than I thought when I looked at it the first time. I just hope that when I was adjusting them I was measuring the right way. I used the smaller of the clearance limits when I adjusted them, but I made sure to slide it in from the front and then both sides. I guess we'll find out... HA!