Gas mileage problem + popping from carbs

[CB900SS]

So I took my bike out for a frigged ride today and was very disappointed in the fuel usage.

I went just over 100 miles and the bike has less than a 1/4 tank left... No I didn't top it off to check the mileage. I didn't beat the crap out of the bike to bad either.

Also the bike is running extremely rich, like instantly burns your eyes if running in the garage. The bike does have pods, I don't know what has been done to the carbs to make them run properly. The bike also seems to have a roughness at all RPM that I don't think should be there.

So what mileage should I expect from an 1150?

I also assume the bike would have more power if it was running leaner.

My answer to this problem will eventually be a set of direct lift carbs...
But I wonder if for now I can adjust the needle position? I don't want to waste money on re-jetting these current carbs.

On another note, when the bike is first started... especially in cold weather... It pops from the air breathers, obviously from compression leaking back through the intake valves... In cold weather and when the bike hasn't been started for a while it pops quite a few times before stopping. On warmer days (70+ degrees?) it only pops a few times and then stops.

When I first heard the bike do this I assumed a valve adjustment would cure it. And when I adjusted the valves and found tight clearances on a few intake valves I figured I had found the problem. All valves have been adjusted within specs and the problem still persists. Is this normal? Should I pull the valve cover back off and re-check the valve adjustment? Maybe they had some serious carbon buildup on the seats and the adjustment has knocked most of this off, driving the valves deeper into the seats, in turn giving me tight clearance again?

Thanks for reading.

 

[not a biker]

my 84 1150 es cold will pop back into the air box a little. in my case the jetting is stock lean. so i figured it needs a jet kit. my guess is you have a carb with a cloged air or fuel jet.carb ballance my be off also. it would have been good to have checked the compression while you did the valve adj . you could have a leaking intake valve. good luck

 

[CB900SS]

do the carbs have a jet kit in them now with the pod filters ? if not they are running way to lean put a stage 3 dynaJet kit and save your self alot of trouble the kit comes with thinner needles and bigger jets that work like a charm cheep free advice

Did you read my thread??

not a biker, the bike has 160psi of compression. Thanks for your reply.

 

[anthonygs1000]

Did you read my thread?? yes and it sounds like a fowled spark plug or wrong jetting or plugged carb. does the bike have a kit in it now ? when you start the bike do all 4 pipes get hot ? is that a 4 into 1 pipe are the filters K&N's

 

[CB900SS]

Did you read my thread?? yes and it sounds like a fowled spark plug or wrong jetting or plugged carb. does the bike have a kit in it now ? when you start the bike do all 4 pipes get hot ? is that a 4 into 1 pipe are the filters K&N's

My bike is running on all 4, it will pull the front wheel in first gear and has plenty of get up and go... But I think it could have more. I actually have measured each header pipe recently with my lazer thermometer, all are very close to temperature.

One thing I have not done is take a plug reading, I guess I will do that next.

If you read my thread you would see that I said the bike came with the pods and I am not sure what the person did to the carbs to make them run "correct". I am not going to waste any money buying jet kits for these carbs, any money going towards the carbs will be going towards direct lifts carbs.

Yes 4 into 1 and K&N. Its getting a kerker 4-1-2 pretty soon, I just need to get them ceramic coated.

Thanks for trying to help.

 

[feelergaugephil]

Is it a pain to start from cold? if so, recheck the valve clearance again.

 

[Nessism]

I'm not familiar with what "It pops through the air breathers" means. Could you explain?

In general it sounds like your bike is overly rich based on your comments and the gas mileage. I doubt the problem is valve adjustment related.

 

[CB900SS]

No, its not hard to start from cold at all. Also a cold compression test told me 160psi on all cylinders.

I agree nessism, but I am going to still double check my clearances... Because a motor popping through the carburetor to me means its leaking compression back through the intake valve/s. I am not sure how I can explain it better at this time.

The bike is certainly overly rich, but I am going to confirm this with a plug reading at different throttle positions.

Thanks.

 

[Nessism]

No, its not to start from cold at all. Also a cold compression test told me 160psi on all cylinders.

I agree nessism, but I am going to still double check my clearances... Because a motor popping through the carburetor to me means its leaking compression back through the intake valve/s. I am not sure how I can explain it better at this time.

The bike is certainly overly rich, but I am going to confirm this with a plug reading at different throttle positions.

Thanks.

Backfiring through the carbs is a common problem that has nothing to do with the valves, although double checking them can't hurt.

Sounds like a mixture problems to me. I'd pull the carbs and make sure they are clean and take an inventory of what jets are in there. From there you can make a more informed decision on what to do next.

 

[Guest]

Popping is from unburnt fuel on the off fire stroke from a rich condition during the choke circuit.
Don't worry about it.

I bet there is already a jet kit in there and it's just set a little rich.
Do the throttle chops as you suggested to find the circuit(s) that are the culprit.

 

[CB900SS]

Popping is from unburnt fuel on the off fire stroke from a rich condition during the choke circuit.
Don't worry about it.

I bet there is already a jet kit in there and it's just set a little rich.
Do the throttle chops as you suggested to find the circuit(s) that are the culprit.

Thanks for this, I hope your right about the unburnt fuel and not leaking valves. I have not done a leak down test yet, but I plan on it just to see if I am under 10%.

But also, it still does this with the choke off.

Do these carbs have an adjustable needle position?

 

[Nessism]

The stock needles are not adjustable per say but you can raise/lower them with shims on top of the clip (there is a spring pushing up on the needle for Suzuki applications so the shim thickness above the clip determins needle height). Since your bike is already rich maybe someone installed a jet kit already. If that is the case, your carbs may have adjustable needles with C-clips.

 

[CB900SS]

The stock needles are not adjustable per say but you can raise/lower them with shims on top of the clip (there is a spring pushing up on the needle for Suzuki applications so the shim thickness above the clip determins needle height). Since your bike is already rich maybe someone installed a jet kit already. If that is the case, your carbs may have adjustable needles with C-clips.

Perfect, your very helpful. Thanks.

In either case I am sure the bike is running rich, at least at idle anyway.

After I take some plug readings I will make a decision on whether to pull the carbs or not. Hopefully before the winter is over I will have some direct lift mikunis and I won't have to waste my time worrying about these CV carbs.

Here is a video of my bike running I made for my boys over at CB1100F.NET.

 

[Guest]

If you have 160# of compression on all cylinders I'd say your valves are sound.
If it was me I'd have those carbs apart to see where I'm at.

 

[hampshirehog]

If you have 160# of compression on all cylinders I'd say your valves are sound.

Seconded (definitely if 160 psi cold). You can hear it's running rich on tickover in the video as well.

For what it's worth, I belong to the school that thinks CVs are sub-optimal unless running with the stock intake and 'proper slide carbs' are the way to go.

 

[argonsagas]

If you have 160psi across all four there should be no problem with valves.

There is a definite problem with carburetors/fuel mixture.

 

[Steve]

I went just over 100 miles and the bike has less than a 1/4 tank left... No I didn't top it off to check the mileage. I didn't beat the crap out of the bike to bad either.

So what mileage should I expect from an 1150?

The only way to check mileage is by starting with a full tank, riding a bit (your 'just over 100 miles' is great) and filling up the tank again. Just watching the gauge on these bikes is an exercise in futility. After some time with the bike you will get to know that when the needle points to a certain mark you will put in about X number of gallons, but you can't read 1/4 on the gauge as 1/4 in the tank. My wife's 850L goes way over the full mark when the tank is full and it takes 30-40 miles to get it to the full mark. Another 50-60 miles and it's at half. About 30 more and it's at the red line. Definitely not linear response.

My answer to this problem will eventually be a set of direct lift carbs...
But I wonder if for now I can adjust the needle position? I don't want to waste money on re-jetting these current carbs.

Why the 'direct lift carbs'? If you are keeping the bike on the street, there is nothing wrong with a set of well-tuned CV carbs. Spending about $30 for a set of jets for these carbs will certainly be cheaper (and easier) than buying a set of carbs for ... how much? ... then spending more money to re-jet them.

My bike is running on all 4, it will pull the front wheel in first gear and has plenty of get up and go...

And there is a problem with this? Sure, when it's better-tuned you might get it up in second or third, but you can achieve that with your present carbs.

The bike is certainly overly rich, ...

You already know it's rich. Should not take much to lean it down. In fact, check the idle mixture screws. Unless you are acellerating or simply at high speed, the carbs spend a lot of time on the idle circuit. If they are running overly rich, it can really affect your gas mileage and overall driveability.

Sounds like a mixture problems to me. I'd pull the carbs and make sure they are clean and take an inventory of what jets are in there. From there you can make a more informed decision on what to do next.

If you read Nessism's sig line, it would make your job much easier. "To measure is to know."

Do these carbs have an adjustable needle position?

Stock ... no. But, do you know if they are stock? No. So far it sounds like you don't really want to know what's in there. You might already have a proper jet kit that simply needs to be fine-tuned.

Hopefully before the winter is over I will have some direct lift mikunis and I won't have to waste my time worrying about these CV carbs.

Hopefully, before the winter is over you can tell us how it turned out.

For what it's worth, I belong to the school that thinks CVs are sub-optimal unless running with the stock intake and 'proper slide carbs' are the way to go.

Everybody is certainly entitled to his own opinion. I belong to the school that thinks that CVs are great for general street use. They do have serious downfalls on the track where there is constant wide-open useage with intermittant closings followed by wide-open again. They just can't handle those transitions gracefully. With either system, you will need to be properly jetted to run well, and I happen to think you could do well with your current carbs, unless you are doing street drags for pinks.

.

 

[anthonygs1000]

Problem identified

Problem identified

this is a Honda guy that owns a real bike now with the old school Honda mentality just hold on bud to catch up to us Suzuki guys you have to crawl before you can learn to fly. seriously don’t be afraid of the carbs
they wont bite you can adjust a valve but worried about simple carbs take them off and take a look you have nothing to loose

 

[doctorgonzo]

Just a note I'll throw out there, be careful of popping/spitting carbs as the fuel can soak your air filter and cause it to catch on fire buring up the airbox and the parts of the harness nearby... ask me how I know.

 

[Nessism]

No doubt, the 1150 has power to be unleashed with the use of free flowing carburetors. The stock engine has plenty of power for most people but some thrill seeker types aren't happy until they have maximized the potential - moving the bike from scary fast, to crazy fast. Nothing wrong with that I suppose as long as you have the money to spend.

Guess this thread comes down to how much work does Mr. Honda want to put into his "slow" stock carbs. Only he can decide this. Personally, I'd work on the jetting in the stock carbs and see what can be done. After the bike is running right a more informed decision can be made relative to the need for more power.