Motor noise on a MKII help needed

[dingy]

Uncledj is having a 'new' noise on his Venture.

 

I can not determine what it is either. It is a somewhat metallic sound in the low end RPM ranges, seems to clear up above 4000 or so when I rode bike.

 

I tried recording a clip of sound on each side with my Iphone, but noise is not very obvious on recording, and the right side clip sounds totally different from left side on recording which is not actual case.

 

He has had complete exhaust system apart with nothing apparent found there.

 

Gary

 

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[mbrood]

Not real experienced with this but it sounds like a lifter problem. Motor oil is up to level?

 

I would put a long screw driver against the head of one bank section on one side and against your ear and rev it, listening for an increased level... repeat for each bank half.

[Yammer Dan]

Do nothavecomputer to listen but i would still bet exhaust.

[mbrood]

It's a solid metalic "tap"... not a rattle or creaking. No sound until it's up around 1500 then follows the rev rate but obviously at a reduced rate which speaks of valves, lifters and such.

[uncledj]

Just got home from Gary's

Gary (Dingy) was kind enough to "put an ear" to it for me, since I don't know what more I can do to try to identify the problem.

As he said, the recording isn't that great, but does give a bit of the offensive sound, but I really don't believe it's coming from the valve train. There may be a bit of ticking, indicating that they should be adjusted, but nothing serious.

The sound seems to be coming from the collector. We inspected the original collector with a fiber optic scope that he had, and could find nothing out of place.

Not knowing what else to do, I got a collector off of Gary, which was originally on"Tweety" and I'll put it on and see what happens.

If that cures it, you can bet that I'll cut the original collector apart to see what's up.

As far as the left exhaust goes, I got hold of a left muffler from a first gen MK I and, although the mount was a little different, I was able to bolt it to the collector and it made no difference.

I'm doing a road trip next weekend and was hoping to have it resolved by then, but if not I'll ride it as is. The bike seems to run well, and the only problem at this point is the noise.

[uncledj]

Just listened to it again, and if you listen to the second recording, you can hear that "Thrush" or "Cherry Bomb" muffler sound when I let off the throttle. That is definitely not valves. It's the rumble that you'd get when the exhaust is ? sucking air in? when you let off the gas.

Again,....can find no exhaust leak.

[KIC]

Mine has a rattle that can change with the higher RPM's...it is some type of heat plate behind the motor and between the motor and the rear shock. Both my 87 and 89 have the bolts "broken through" or worn through, the metal plate that rattles louder as you accelerate.

[frankd]

DJ and Gary,

 

If the exhaust chamber isn't the problem, consider the following.

 

I've ridden my bike about 50 miles since I've fixed my carb diaphragms and I still can't get over how quiet and sweet it sounds. I had the 83 here a month ago, and everytime I road it, I couldn't get over how smooth it sounded. My 89 sounded harsh and rough by comparison. But the kicker was when I had the temporary repairs done to my diaphragms done (3 had holes), when I started it back up it sounded like it was coming apart when it was idling. I had to convince myself that nothing was wrong with the motor, that it must be the carbs I just messed with. I hooked up the vacuum gauges to sync. the carbs, and both right cylinders had real high vacuum--I had to open up those carbs quite a bit to sync it. With all 4 cylinders equal, it sounded great. It's a lot quieter going down the road @ 65 MPH also. When all 4 cylinders aren't firing equally, the motor speeds up when a strong one hits, and then slows down when the weak one(s) fire. This causes rapid speed changes in the motor, and the play in everything spining going back and forth makes strange noises. When you have 4 equal cylinders, the speed doesn't change up and down as much.

 

Check the carb syncronization, and if it's off more than a little, check the diaphragms. It's a small thing to do considering all the time you've spent already.

 

Frank D.

[dingy]

I think he just changed diaphragms and checked the syncing within last couple of days.

 

So far the one reply that sticks in my mind as being like the sound was what KIC said about the rear heat shield. It seemed to be like a rattle type sound more than an engine or lifter knock. And, the noise seemed to originate from the front of motor when I rode it and when standing by it.

 

The valve train was a little noisier than what I thought normal, but not real bad. The motor was at operating temp when I saw it.

 

Gary

[uncledj]

It was the collector...!!!!

Don't as me to explain it. As I said, I saw nothing wrong with it, and we even looked inside with a fiber optic camera and saw nothing out of place. I put the collector from Gary's bike on it, .....had to make a gasket for one of the mufflers since I couldn't get the old one off intact, put it all together and WALLAH...no more noise.

The warden (wife) is disappointed that I've been working on the bike all day (again), so we didn't get to do anything today, so I'll have to spend time with her tomorrow, but you know I'm chomping at the bit to cut the original collector apart for a look see.

I'll let ya'll know what I find....Might not be 'till next week though.

The important thing is I'm ready for next weeks road trip without any issues...YIPPEE!!!

I know it gets said a lot, but what a great site, and what great, knowledgeable people, so willing to help.

A special thanks to Gary....I owe ya one brother.

Thanks everyone for the advice on this issue.

I gotta go pick up the tools and get cleaned up before the wife leaves me...LOL

 

[frankd]

You'll probably find one of those screens that has broken loose at one end.

 

Frank D.

[Yammer Dan]

Collector? Is that part of the exhaust? Loose baffle in collector will be what you find. Take them all out. It probably won!t happen again.

[uncledj]

I'll see if I can post pics when I cut it apart

Anyhoo, here's what I've done during this minor teardown.

Replaced the collector

Replaced spark plugs

Replaced plug wires

Replaces carb diaphragms

Synced carbs

Replaced clutch slave cylinder

Changed clutch fluid

Replaced rear brake pads

Changed all brake fluid, / bled

Greased splines

Changed final drive oil

Changed engine oil

Repaired broken tab on lower fairing

Installed forward foot rests

Polished any aluminum / chrome I could get at.

 

Should be ready for a trip

I'm not looking forward to replacing the TCI when the next group buy happens....looks like I'll just about have to remove the fairing to change that.

 

That was enough wrenchin' to last me for the rest of this Summer.

[dingy]

I'm not looking forward to replacing the TCI when the next group buy happens....looks like I'll just about have to remove the fairing to change that.

 

That was enough wrenchin' to last me for the rest of this Summer.

 

You don't have to remove fairing to put aftermarket one in. The cables can be unplugged from the old one and leave it in place and put new one one top of air box. This is related to the hand size thing we discussed.

 

I might also have a spare side stand switch if you ever want to fix that. Bike is not supposed to crank in gear with side stand down.

 

Gary