Top end query;

[XSokieSPECIAL]

XSokieSPECIAL said:
These bikes are built to run on REGULAR gas! Try Chevron or Union 76 fuel, or NO MORE than midgrade from a lesser company. The problems I am reading, including the extra heat and noise at high RPM, is running lean, IMHO. As TC said, run it on prime for a test, and see if it still has problems. If it does, it's NOT the octy, but probably the jetting. I would go up one size on the main, and drop the needle back down to the middle position. The other thing you may want to do is raise the float about 1mm, say 27 instead of 28, to allow a little more fuel in the bowel. this will also make it run just a little richer in ALL RPM ranges.

I just got back from a short run with the mix of reg. and prem. and the noise is almost gone.

I know these engines are designed to run on regular , but 1980 regular was a whole lot different from 2010 regular. The damned thing runs like a raped ape on the regular but it sounds like it's gonna grenade at any moment.

I think, if I remember correctly, the floats are set at 27.5 because that was the only way I could correct the flooding at idle problem I had with these 79 carbs to begin with.

I might try raising the main needles another notch before I rip the carbs back off 'cause I think I can do that right on the bike. Pulling the carbs with the stock airbox is a real PITA.

It actually runs pretty damn good the way it is but I like stuff to work pefectly. I'm just funny that way......

[XJOK2PLAY]

I just got back from a short run with the mix of reg. and prem. and the noise is almost gone.

I know these engines are designed to run on regular , but 1980 regular was a whole lot different from 2010 regular. The damned thing runs like a raped ape on the regular but it sounds like it's gonna grenade at any moment.

I think, if I remember correctly, the floats are set at 27.5 because that was the only way I could correct the flooding at idle problem I had with these 79 carbs to begin with.

I might try raising the main needles another notch before I rip the carbs back off 'cause I think I can do that right on the bike. Pulling the carbs with the stock airbox is a real PITA.

It actually runs pretty damn good the way it is but I like stuff to work pefectly. I'm just funny that way......

Sooo....
Are we goin' riding this evening? Say... between 7:30 & 8:00?

[TopCatGr58]

Hey Greg,

I hate to ask, don't remember if you've stated it or not, but what do you have the Vacuum advance hose connected to? The #2 carb body metal nipple, or the Intake Boot synch port/nipple? The vacuum advance shouldn't be making that kind of noise with the METERED vacuum from the #2 carb body, but it CAN do that if getting direct vacuum from the intake boot!

Well, like Diver said, you've most likely ruled out fuel starvation from the OCTY, but haven't ruled it out via too small of jets! Moving the slide needle won't help, because it's up quite a bit when you are throttling hard trying to get it to accellerate. The needle controls the transition from pilot to main circuit. Raising it possibly move that transition to a lower rpm range which may not be good. However, it still won't let anymore fuel come thru the main jet under hard throttle than what the main jet can provide.

T.C.

[XSokieSPECIAL]

Sooo....
Are we goin' riding this evening? Say... between 7:30 & 8:00?

Gimme a call Bob, I'm not seein' a problem.

Hey Greg,

I hate to ask, don't remember if you've stated it or not, but what do you have the Vacuum advance hose connected to? The #2 carb body metal nipple, or the Intake Boot synch port/nipple? The vacuum advance shouldn't be making that kind of noise with the METERED vacuum from the #2 carb body, but it CAN do that if getting direct vacuum from the intake boot!

Well, like Diver said, you've most likely ruled out fuel starvation from the OCTY, but haven't ruled it out via too small of jets! Moving the slide needle won't help, because it's up quite a bit when you are throttling hard trying to get it to accellerate. The needle controls the transition from pilot to main circuit. Raising it possibly move that transition to a lower rpm range which may not be good. However, it still won't let anymore fuel come thru the main jet under hard throttle than what the main jet can provide.

T.C.

It accellerates great! It's just when I get into the upper 2 gears at high speed I get the spark knock/preignition sound. It seems perfect all through the range exept there. It may just be the gas I'm using.

I don't remember having this problem when it was cooler out and I had the other exhaust on. So, I'm thinking it will be a minor adjustment for the temp change.

I'll try some fuel from another source and see what happens. Lots of variables here.

[XSokieSPECIAL]

Ok, my engine is still making noise. The more I listen to it the more it sounds like a piston or wrist pin knock.

At idle on up to between 3 & 4k it's quiet then it starts, and it's pretty much all the time on the highway.

Crazy thing is I put my stethescope on it at work and it's loudest at the ignition cover. I'll drive the Blazer tomorrow and tear the left cover off wed. and have a peek inside.

Any ideas?

[petejw]

hi greg,
was just reading back a couple of posts,
i think you have the float levels to low (lean)
stock settings are 25.7, ive found on my bike if you set
the floats at half mm on the lean side, it fixes that flooding at idle.
having a really lean float level isnt a good thing, youre also having to rejet
to make up for the leaner mixtures throughout the range, which you were thinking of doing by raising the needle, imo id set the floats at half mm on the lean side, then start with checking the mains then needles.
have a look at the factory pro site to set the carbys up

http://www.factorypro.com/tech_tunin...m_engines.html

i cant find the one for lower revving engines, but the principles are the same.


regarding the engine knock, ive got a clapped out main bearing on mine,
which starts to knock once the bike warms up, the sound can be heard from
the ignition cover, but the knock can be heard from idle up.
you can sometimes isolate a knock by removing a spark plug lead 1 at a time, this can help you identify what cylinder is causing the knock.

jat your not running irridium spark plugs are you?

[Ivan]

regarding the engine knock, ive got a clapped out main bearing on mine,
which starts to knock once the bike warms up, the sound can be heard from
the ignition cover, but the knock can be heard from idle up.
you can sometimes isolate a knock by removing a spark plug lead 1 at a time, this can help you identify what cylinder is causing the knock.

jat your not running irridium spark plugs are you?

Just a small hint. On a waste spark engine, pulling one plug kills two cylinders. A better way to check it is to clamp a test light to ground and then back probe the boot of the cylinder you want to check. It gives the spark a place to go without killing the sister cylinder.

[XSokieSPECIAL]

hi greg,
was just reading back a couple of posts,
i think you have the float levels to low (lean)
stock settings are 25.7, ive found on my bike if you set
the floats at half mm on the lean side, it fixes that flooding at idle.
having a really lean float level isnt a good thing, youre also having to rejet
to make up for the leaner mixtures throughout the range, which you were thinking of doing by raising the needle, imo id set the floats at half mm on the lean side, then start with checking the mains then needles.
have a look at the factory pro site to set the carbys up

http://www.factorypro.com/tech_tunin...m_engines.html

i cant find the one for lower revving engines, but the principles are the same.


regarding the engine knock, ive got a clapped out main bearing on mine,
which starts to knock once the bike warms up, the sound can be heard from
the ignition cover, but the knock can be heard from idle up.
you can sometimes isolate a knock by removing a spark plug lead 1 at a time, this can help you identify what cylinder is causing the knock.

jat your not running irridium spark plugs are you?

Mine the sound does get louder when things warm up , but at an idle on up till 3 or 4 k it seems fine. Except when I'm in higher gears (4th or 5th) at cruising speed it seems pretty loud.

I tried the pulling plug wires trick earlier but at a stand sill it won't hardley do it at all. I really have to play with the throttle then.

It pretty much has to be in gear under power to get anything significant.

Just a small hint. On a waste spark engine, pulling one plug kills two cylinders. A better way to check it is to clamp a test light to ground and then back probe the boot of the cylinder you want to check. It gives the spark a place to go without killing the sister cylinder.

Thanks Ivan, I'll remember that. Never noticed it working that way in automotive though.

[bikerphil]

My old \'79F motor had a knock similar to what you are describing, I ended up running straight 70 in it and it was good for another 25K that way. It was a bear to crank on a cold 45 deg. Florida morning though. I\'d check for a broken timing advance spring, maybe it\'s advancing too soon.

[petejw]

hey ivan,
i understand about the wasted spark,
but having 1 cylinder foul wont cause the other
one not to spark, i just went out side to test that theory,
i pulled no 1 lead and put a spark plug and earthed it to the engine,
i removed the no 4 lead and put a phillips head screw driver inside the cap and earthed it to the engine,
the no 1 cylinder still sparked. you can also just disconnect 1 lead while the engines running and the engine will still run on 3 cylinders.
the time i had the plug lead just off the spark plug i was riding it home
to keep the cylinder firing.

hey pil,
im running 40 - 70 oil atm and with winter here,makes for interesting starting, especially when the starter clutch slips.

hey greg,
jat, have you synced the carbs?
also if you have vac guages, have them connected and rev the engine and see if theres any differences between cylinder readings.

[XSokieSPECIAL]

Yea pete, I just synced them before I rode to Bob Jones. This all just started sunday when I pushed it hard.

I have been thinking there was a strange rattling noise coming from the left side cover for a while now. That'll be the first place I'll explore, advance components under the breaker plate.

If nothing there, oil pan to see if anything dropped down in there that'll give me a clue.

Then the head and jugs and look at the pistons and wrist pins. Sound logical?

I might get lucky in one of those places but if not, he11 I'll have the engine halfway pulled and tore down already.

[xj11john]

I had a terrible engine noise on my XJ a few years back and I took it to the local small engine/motorcycle repair shop. The guy kept it for two weeks (I'm not sure how much he looked at it, but said he could'nt figure it out) I then checked on here, and found that the cam chain will make a similar noise, I called him and told him, and sure enough that was it.

So he just adjusted the tensioner, and that was it. (about a 10 min. job)

He still charged me an hour labour, needless to say I have'nt let him do much other than a sync, and put on tires (he has a tire machine), since.

So you might check that just in case, JAT.

Good luck!

[XSokieSPECIAL]

Thanks John but I have the venture auto tensioner installed.

Pulled the pan tonight and foud quite a little sparkling goin' on.

There's copper and brass in that thar pan........

[petejw]

thats not good,
theres a lot in there, at least you got to it
before you spun a bearing, which ive done,
hopefully your crank and conrods are ok, and you can get away
with just replacing the bearings.

[psycoreefer]

for the price of bearings you can buy a whole bike if you keep your eyes open. Kinda disappointing...wonder if there are any "generic" rod/main bearings that would work instead of the $$$ Yamaha ones?