Very rich smelling exhaust

[s.tyler58]

So here's the deal, my 83 in my estimation is running quite well this summer. However my exhaust smells very rich and my gas mileage is around 30 to 32 MPG. It does sound as if there's a very slight popping at highway speeds but not like a consistent miss or not firing cylinder. Having never been around another V4 or having anyone with experience with them around give me advice. I really wish someone could ride this thing and tell me how I'm progressing and how I can get rid of that seemingly wasted fuel somehow. Carburetors we were rebuilt this winter and synced a couple months ago and have remained consistent. Like have said before, as far as I know she's running hard and fast when I ask her to so I'm puzzled by the why it would smell like that. Smells like full choke exhaust or something.

 

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Edited August 22, 2018 by s.tyler58

[suds]

I'm interested to see what the experts say on this one because I'm wondering the same about my 90 VR.

 

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[BlueSky]

Try leaning out the idle mixture screws a tad. An exhaust analyzer is needed to set them correctly. And some have added a thin washer to the diaghragm shafts to lean those out. Cowpuc added some to Tweeks a few years ago. You might find the thread if you do a search. The enrichment diaphragms could need replacing too maybe?

[s.tyler58]

Try leaning out the idle mixture screws a tad. An exhaust analyzer is needed to set them correctly. And some have added a thin washer to the diaghragm shafts to lean those out. Cowpuc added some to Tweeks a few years ago. You might find the thread if you do a search. The enrichment diaphragms could need replacing too maybe?

I'll have to check my parts list from my mechanic but I was pretty sure he put all new stuff into my carbs in January.

 

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[Karaboo]

Try Skydocs shim kit.

[Patch]

So here's the deal, my 83 in my estimation is running quite well this summer. However my exhaust smells very rich and my gas mileage is around 30 to 32 MPG. It does sound as if there's a very slight popping at highway speeds but not like a consistent miss or not firing cylinder. Having never been around another V4 or having anyone with experience with them around give me advice. I really wish someone could ride this thing and tell me how I'm progressing and how I can get rid of that seemingly wasted fuel somehow. Carburetors we were rebuilt this winter and synced a couple months ago and have remained consistent. Like have said before, as far as I know she's running hard and fast when I ask her to so I'm puzzled by the why it would smell like that. Smells like full choke exhaust or something.

 

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Likely Steven (1200cc)& Suds (1300cc) there will be no magic bullet unless you both have incorrectly set enrichers?

 

Steven, is the present gas mileage better, same or worse then before the rebuild?

 

Sure you both know my posts well enough to know, I am a base line troubleshooter.

 

Important to know what the compression is, nothing fancy, just cold cranking, note the reading at 5 revolutions but allow the rpms to max out, in other words what is the maximum pressure when the needle stops climbing.

The reason for the 5 count, (I'm just sharing) is the difference between quick or slow build pressures. (sealing capacity)

 

What is the mileage for both bikes?

 

Steven do you know if they used a stock rebuild kit? Or up sizes?

 

Simple question, are both air filters in good working condition?

 

Steven are you able to measure your coils?

[Patch]

PS. The popping Steven needs to be sourced.

 

Lash checked? Might get a hint from the compression test..

Could also be carbon build on the seats.

 

Ever pop up thru the air box?

[s.tyler58]

Whew!

 

41,000

Better. I ran out of full fuel tank twice at 125/128 miles last year. I stopped carrying a gallon this spring because pretty consistently at 155 I had better have a plan.

 

Stock OEM rebuild kit.

 

Air cleaner in good shape.

 

No on the popping out of air cleaner.

 

I have never measured compression or coils before but might be able to borrow devices needed to do so for the first time. I'm hesitant to reply to your question with, I'm not able! I'm just inexperienced.

 

New in January, wires and caps. Valve's adjusted and gaskets replaced.

 

Running red TCI unit out of the Netherlands.

 

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[BlueSky]

This training video shows carb adjustment.

 

[Patch]

"I have never measured compression or coils before but might be able to borrow devices needed to do so for the first time. I'm hesitant to reply to your question with, I'm not able! I'm just inexperienced."

 

Funny guy, the only challenge for the compression test is taking the time to properly thread the adapter down thru the threads.

 

We are seeing more often as these bikes age failing coils. Really the voltage test at the 2 terminals and that inexpensive gap tester connected to the coil and the spark plug will allow you to see what is going on through the rpm range say up to 4000ish

 

Please take care not to get a jolt while testing, stop the bike when or if you need to increase the gap.

I always run a fan when testing the bikes.

 

And have fun!

Edited August 24, 2018 by Patch

[BlueSky]

Something to check is the spark plug wire where it screws into the cap. The copper core wire tends to corrode and usually snipping off 3/4" of wire and screwing it back in resolves the issue.

 

My bad! I didn't read where you replaced the wires and caps! Have the valves been adjusted recently?

Edited August 23, 2018 by BlueSky

[s.tyler58]

Something to check is the spark plug wire where it screws into the cap. The copper core wire tends to corrode and usually snipping off 3/4" of wire and screwing it back in resolves the issue.

 

My bad! I didn't read where you replaced the wires and caps! Have the valves been adjusted recently?

You're bad again! Hahaha! I also wrote that the valves were adjusted in January or winter. With new valve cover gaskets. Although, sound of the valves on my number 2 cylinder seem somewhat chatty.

 

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[snyper316]

PS. The popping Steven needs to be sourced.

 

Ever pop up thru the air box?

 

Mine is? Mainly when I first start it then under load... Hope you got answer for that.

 

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[snyper316]

Ps just started that popping. Last week... Checked my plugs and they look good no sign of lean or rich for that matter.

 

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[Patch]

Mine is? Mainly when I first start it then under load... Hope you got answer for that.

 

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Hi Snyper, can you tell where the popping is coming from? Intakes or exhaust

 

I can certainly share some thoughts on it. Often what is being described is the difference between a cold & hot valve!

If there is even mild pressure above the valve it will not seat fully which allows for a minor compression leak to slip by the mating surface. And as you likely just guessed, when the valve warms it expands in all directions but logic would suggest that valve mass will offer more expansion.

Smarter then myself metallurgist and machinist study and know what to expect, they decided how best to machine for... then forward us common folk what the specs are, wisely we follow their advice;)

 

Could also be a little bit of carbon around the seat? This sometimes is temporary in that it clears itself or gets hammered into the seat angles at high temperatures.

 

Another cause can be corrosion; this is more common when bikes have not run for a long time. This can cause pitting you'll reach that conclusion only after you first: check lash, perform some decarbonizing, and run the crap out of it over a weekend ride.

 

Setting up to take your best guess would start with compression testing cold first, then as hot as you can work with. Or, some might choose to do a leak down test. But we are looking for both readings in such a case. If all the numbers came at lowish then we might try wet testing as well, the mileage and ownership would influence how to move forward.

 

I didn't mention a possible bent stem because, as you mention it corrects at operating temp.

 

My old Suzie's cough when cold, I think every old one that I've worked on has or still; but quickly seal after a minute or so.

 

Check lash is a good starting point or compression test

Patch

[snyper316]

Hi Snyper, can you tell where the popping is coming from? Intakes or exhaust

 

I can certainly share some thoughts on it. Often what is being described is the difference between a cold & hot valve!

If there is even mild pressure above the valve it will not seat fully which allows for a minor compression leak to slip by the mating surface. And as you likely just guessed, when the valve warms it expands in all directions but logic would suggest that valve mass will offer more expansion.

Smarter then myself metallurgist and machinist study and know what to expect, they decided how best to machine for... then forward us common folk what the specs are, wisely we follow their advice;)

 

Could also be a little bit of carbon around the seat? This sometimes is temporary in that it clears itself or gets hammered into the seat angles at high temperatures.

 

Another cause can be corrosion; this is more common when bikes have not run for a long time. This can cause pitting you'll reach that conclusion only after you first: check lash, perform some decarbonizing, and run the crap out of it over a weekend ride.

 

Setting up to take your best guess would start with compression testing cold first, then as hot as you can work with. Or, some might choose to do a leak down test. But we are looking for both readings in such a case. If all the numbers came at lowish then we might try wet testing as well, the mileage and ownership would influence how to move forward.

 

I didn't mention a possible bent stem because, as you mention it corrects at operating temp.

 

My old Suzie's cough when cold, I think every old one that I've worked on has or still; but quickly seal after a minute or so.

 

Check lash is a good starting point or compression test

Patch

Well the popping is on intake side. I pulled plugs and the have a nice tarnish color like they should. I am thinking maybe time to check valve lashes and shim her up. But I would be interested in your thoughts also. I just hope I haven't broke the motor and whatever the cause is fixable because I believe her miles to be accurate 26000. Or soon will be. Which means I have put about 10000 on her since getting her up and going almost 2 yrs ago.

 

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[Patch]

Well the popping is on intake side. I pulled plugs and the have a nice tarnish color like they should. I am thinking maybe time to check valve lashes and shim her up. But I would be interested in your thoughts also. I just hope I haven't broke the motor and whatever the cause is fixable because I believe her miles to be accurate 26000. Or soon will be. Which means I have put about 10000 on her since getting her up and going almost 2 yrs ago.

 

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Yep that pretty low mileage Snyper, not sure all that is going on but cam't be much wrong, these Yamaha Ventures are very well built!

So I think the compression test will expose some truth, also even though the miles are low we can't rule out lash, so for me it's always a compression test regardless of who owns or mileage when it come to older bikes.

 

I'm going to be posting in general a something that happened last Sunday, so a relatively new but zip mileage Kawa not unsimilar except she was flaming about 6" above carbs... Other stuff as well need to get my English straight and write it up.

Keep us in the loop,