Hollow rattle, and a pop

One problem fixed, another remains.

As a reference for anyone else with this issue.. The bike would start up fine, but quickly run up to 4000rpms and stay there. I checked that the butterflies were fully closing after reading another thread on here, and they were. Stuck, I examined the butterflies a bit closer. Turns out after cleaning the carbs, I installed one of the valves in upside down. The edge of each valve is close to 90 degrees, but not quite. More like 85/95. So yeah, now I can synch the carbs.

However, once I get up past 2K rpms, I hear a hollow rattle like sound from the engine or transmission. Not sure what it is, but it doesn't sound friendly. The bike's in neutral, on the center stand, when I rev it up. Haven't ridden it yet with the recent issues. Is this something to be concerned about? Will a good synch eliminate this issue?

Another issue, I'm getting some popping noises from the engine and exhaust. My initial assumption is that I'm running rich, but with a DynoJet kit and no colortune, I can't be sure. Suggestions?

Thanks guys.

 

According to the web site you have an Automatic Cam Chain Tensioner on that Bike.
Pull the Left Side Crank Cover.
There a Square 17mm set of flats on the end of the Rotor.
Pull the Plugs and Wrench the Bike two Full Revolutions in its regular motion.
Clockwise.
Come to a slow and gradual stop.
Then, ... Reverse direction and rapidly turn the Engine over Counterclockwise.

The slack in the timing chain will present itself in front of the Tensioner.

If you can have someone lightly tapping on the end of the Tensioner with the butt end of a hammer handle while you reverse direction of the engine the Tensioner should take-up the slack in the Chain and rid the Engine of the rumble.

 

I'm afraid I don't understand. I grabbed a 6mm Allen wrench and rotated the crankshaft twice (similar to the procedure when checking valve clearance). But the crank doesn't turn over as carelessly as I would expect from your advice. There's points of high resistance, then points of low resistance, so I can't turn the engine at a constant rate. Thinking about it now, that doesn't sound good..

 

Did you pull the Plugs?

6mm ??? The Crankshaft flats are 17mm!

I think you might have done something other than what I had expected you to do.
I don't know what, though.

Can you get a hold of a Manual?

That would be the safest thing to do.
I don't want to not be on the same page and have you do something that could have an adverse effect on what we are needing to do.

 

I'll gather some photos and intel and report back to this thread, and I won't fire up the bike until I know we're on the same page.

 

might be a rattle where your exhaust meets your headers

 

Ok, here's a shot of the engine's left side. The top bolt, 6mm, I'm supposed to spin when checking valve clearances. This is the bolt I thought you meant. Then there's the bottom hole for an Allen wrench I'm seeing, which looks closer to the 17mm you mentioned (I originally assumed that was a typo).



I didn't pull the plugs, because the build-up of pressure in the chambers didn't even occur to me until later..

 

Top arrow.
The square fitting surrounding the Allen Head
That square fitting is for Jacking the Crankcase over.
Not the Allen
The Allen is supposed to remain tight.
That Allen secures the Rotor to the end of the Crank.

Put a 17mm wrench on the flats of that square fitting in the top arrow,
The, you can get some leverage on the Crank to move it back and forth without loosening anything.

The Bottom Arrow is a Cap for the Oil Gallery.
Leave that in there ... its supposed to be tight.
Theres oil on the other side of that Lower Gallery Plug.
Don't break it. They are fragile.

 

Cool, I didn't think that bottom one was something I should be messing with. I'll give this a shot and report back.

 

Ok, so I think I managed to reset the tension on the cam chain. However, I'm getting some popping sounds from the engine/exhaust. The closest thing I can really relate it to is the sound during engine breaking on my mustang, but this occurs under acceleration, idle, all times. I assume I'm running rich, and that some of the fuel isn't combusting until it gets to the exhaust, but I don't like to assume much of anything.. I have no colortune and still trying to fully sync the carbs.

 

That's something you will have to tune out.

Read the Plugs and adjust the Pilot Mixtures for Light to Medium Brown on each one.
Some might need more than others. You might have one or two that need no adjustment.

It all depends on the Plug Read.

 

I had the constant popping just after I bought my 750. No inline filter was fitted, hadn't found this site yet, and ended up with 4 carbs caked with rust. Also did the same after fitting pod filters before i got the pilot mixtures setup better, It sounds like it may be running a bit weak.

 

Carbs are good, and I have an inline filter, so I hope those aren't issues.

Rick, assuming I start with a clean plug, how long to I run the bike before pulling and checking the plug? I can already tell this is going to be a fun process...

 

Not long.

I take my bike out to an Industrial Park and run two laps and do a Plug Read.
Thats enough time to tell if its going to be Lean or Rich.

Remember: If you are CLOSE ... the right spot is within a few degrees either way.

 

listen to Rick, get the RPM's up hit the kill switch read the plugs, a lean reading will cause popping from the exhaust

 

ok, I bumped up the fuel in the mixture and the popping disappeared (huzzah!). Managed to sync up the carbs, so the manometer's readings are dancing next to each other. I still need to fine tune the fuel mixture.

But another issue has popped up. The bike sounds like a friggin' lawn mower. It idles fine, but has a very rythmic exhaust note. When I give it throttle, the rhythm becomes more pronounced, along with a severe lack of power. Sounds like a lawn mower..

Would this be due to the fuel mixture alone, or another issue? I tested the mixture from rich to lean, all giving the same rhythmic effect.

 

I think you have rusty headpipes and the rattle you hear is one of the inner liners slapping about against an outer one.

 

the headpipes are definitely rusty, but the rattle was coming from the engine/transmission area. Perhaps once these issues are solved, I'll be able to hear the headers rattling...

 

I'm getting the popping sound (your saying lean, but I also have a strong fuel oder like I'm running rich.

 

I had that same strong fuel odor. However, bumping up the fuel in the ratio did indeed get rid of the popping. Don't remember if the odor is still there or gone..

I'm going to try swapping in new plugs this evening. Perhaps the severe carbon fouling is destroying their efficiency? But I'm also a bit confused at how they can be so carbon fouled when my mixture was lean..