Carb Experts - Round 2

[mcgovern61]

Last year I had an issue with my carbs leaking when the bike was off and the gas petcock was closed. They had been rebuilt the previous winter by a professional. (NOT ME!) I found the floats all out of adjustment and the the float pins not sealing. I readjusted and cleaned the ends and finally got them to stop leaking.

I had an '81 engine with over 169k miles in the bike then and had problems with hesitation and what sounded like a detonation pop when I got on the throttle hard after already getting into 2nd gear at 2500 RPM. This engine also has the infamous knocking/tapping sound at around 3000 rpm on up. I swapped out the engine with a really good '83 engine and never looked back........until I finally started to open up the '81 to see what could have caused that knock!

NOW, here are my carb questions:

* The PO said the "carbs were rebuilt and re-jetted" on the '81 engine when I bought that bike as a wreck. If the new "JETS" are not correct for the carbs ....or... they are aftermarket junk, what would I expect would happen? (Mind you, I am not good with carbs or gasoline engines!)

*The carbs leaked a lot (under statement)....potential cause of knock from too much gas prematurely getting into the intake?

*I did finally check the vacuum advance and it is working fine (although sitting on the floor now).

Take a look at this picture of #3 piston. Is that an excessive amount of burn on the crown? Detonation?

I put the carbs on the '83 engine after all of the leaks and cleanup were completed and it runs good. But could it run better if the jets were changed out and OEM jets installed?

 

[mcgovern61]

I also need to add that when taking apart the heads I found that the #3 intake valve spring is real easy to compress compared to the other valves and the knocking/tapping seems to be loudest at #3 cylinder while riding. I am in the process of checking the oil scavenger pump inlet to see if that may have starved the engine for oil at high rpm (as soon as I get a clutch nut removal tool!)

Also, looking at the #3 exhaust valve, it is real whitish/tan but the port is loaded with carbon.

Picture:

 

[dan filipi]

I'm not a pro with carbs but I have worked on many.
Others may disagree but I believe a jet is a jet. As long as they don't leak past on the threads and the jet size (diameter, length etc.) is the same as stock what the rack and engine calls for then they should be fine.

I'm not sure about the black on the piston and valves but that looks to me like normal carbon build up.

 

[scdmarx]

Your photos don't look that bad to me. Some carbon collecting is normal. Excessive amounts would indicate a rich mixture, oil burning, incomplete burning of the air/fuel mix as a result of something like low compression, too rich-too lean, etc. Periodic cleaning is a good thing. Now that you have the heads off you can loosen it up with some carb spray and wire brush it. Or while the engine is running, inject some water to steam clean the piston top and combustion chamber. But this does nothing for the back of the valves. This will require the use of a chemical on a running engine. Gas tank additive is probably the most convenient way to keep up with carbon build up. But then, now that you have it apart, you can disassemble the head and wire wheel the valves on a bench grinder. Excessive carbon build up on the back of the valves will cause a couple of things. For one, enough build up will cause a restriction, as well as affect flow patterns. On the back of the intake valve it can act as a sponge, absorbing gasoline molecules, leaning the mixture on the way to the cylinder. It can also retain enough heat to actually start ingniting the mix on the way into the cylinder. Any of this will rob your power potential. I can also break loose a chunk at a time and become lodged behind a valve and not allowing it to close, resulting in a misfire. Just what you need while trying to pass a truck on a two lane highway, huh?

 

[AApple]

I agree...don't look all that bad to me, either. I think there may have simply been a mixture issue on the cylinder with the darker color on the piston. Don't see a lean OR overly rich indication...possibly a crappy tank of fuel at some time. Do you use Seafoam at all, or regularly? That would prolly help keep the carbon deposits in check a little better. You can't always believe what the PO tells ya....

 

[mcgovern61]

I agree...don't look all that bad to me, either. I think there may have simply been a mixture issue on the cylinder with the darker color on the piston. Don't see a lean OR overly rich indication...possibly a crappy tank of fuel at some time. Do you use Seafoam at all, or regularly? That would prolly help keep the carbon deposits in check a little better. You can't always believe what the PO tells ya....

I have used Seafoam in that engine numerous times. I did not start using ATF until after the '83 engine was installed. So....if I understand you guys correctly, the engine doesn't show abnormal signs of wear or tear from gas or mixture issues?

I have not found that the pistons seem to be loose on the bearings when I thought for sure the lower end of this engine was shot. (I really expected to be able to feel loose bearings by pushing on the pistons after TDC) And it appears that even though the carbs were not quite right, no serious damage is evident. Maybe this is just a tired engine? (BTW, I did find the compression readings and all four were 160's before the engine swap.) :swoon:

Lastly....I should not be concerned about the jets not being OEM? :?:

 

[joedrum]

to me it shows signs of the exhast being pluged up .....it seems to show good burn in the cylinders and just passed that it anit moving good ....ithink a lot of wings suffer from this .....the science behind mufflers and back pressure is a bunch of bs ...thruth is free low is the best exhast with staged expansion....on the mongruel the exhast was open and guted with 4" pipe that ran back ....i just hack it together with the cross over tube still in use .....that with other things done the mongruel gained a lot of power.....when i took the motor out of the mongruel i look in the exhast ports and it looks nothing like that .....

if you had a dyno on a motor and equal lengths of pipes running to a collective expansion pipe you could mess with to length of the pipe to get the maxium draw on the exhast to match the cam the motor operates with through its torque cruve...and the dyno would tell you so right to the inch in length if it was any good.....nothing to do with stopping flow just controling it .....the only thing worst than muffler teck is catalactic converter teck it never last and gose off from the way it was design to operate rather quickly unless you have computers to keep everything perfect....a well tune free flowing exhast just works period and never clogs up and never makes heads look like that gerry

 

[mcgovern61]

to me it shows signs of the exhast being pluged up .....it seems to show good burn in the cylinders and just passed that it anit moving good ....ithink a lot of wings suffer from this ....a well tune free flowing exhast just works period and never clogs up and never makes heads look like that gerry

Joe, the '81 engine was running with the aftermarket Jardine exhaust the entire time I drove it. When I swapped to the '83 I put on OEM exhaust. The '83 pretty much runs like a clock! Brings up another question....is there a difference between '81 vs '83 carbs? I installed the '81 carbs on the '83 after I did all of that adjusting to get the gas to stop leaking.

 

[joedrum]

after looking at those pics again im not to sure what i was looking at i must have been seeing things ....like apple siad it dont look that bad ...sheeesh sometimes i cant beleave myself.....on the question of the carbs they are the same except for the 80-81 carbs have pressed in jets and the 83-83 have screw in jets ...when you were here i didnt see anything wrong with the way it ran ...it ran fine ...realy fine in my opinion gerry.... :mrgreen:

 

[mcgovern61]

...when you were here i didnt see anything wrong with the way it ran ...it ran fine ...realy fine in my opinion gerry.... :mrgreen:

Yea! That was the '83 engine and it does run good. Just trying to narrow down whether the carb setup may have been contributing to the '81 engine knock.

 

[slabghost]

Yes carbs can contribute to a knock. Usually combined with an ignition issue. Check the ignition on that motor. The mechanical advance and the vacuum.

 

[jdegase]

I found that the #3 intake valve spring is real easy to compress compared to the other valves and the knocking/tapping seems to be loudest at #3 cylinder while riding.

weak valve springs will cause a strange sound sometimes like a knocking... you will probly not hear the lifter rattle your more likely to hear the engine fireing around the valve back into the intake.
also this will cause the valve to burn across the seat.
new springs, or good used springs should fix this pretty easily.

in my opinion you dont have much carbon buildup on the piston, and the exhaust valve can be cleaned up.

 

[Andyb]

I don't have any experience with Goldwing jets, but I have read that some replacement jets are not as good as the oem. I do know that with my old Bandit that there were two versions of the aftermarket needle jets which had different hole patterns. One worked well and the other did not.