how easy to remove carbs?

[formerhondaman]

I have an st1100 aw 1998 abs bike ( abs is debateable lol) 34k miles

It is getting 140 miles to a full tank oof fuel. this is not good. I have changed the air filter the engine oil and the brakes are not rubbing. when I changed the plugs they were black, all of them which would suggest a fuelling problem which would suggest carbs. oh I forgot to mention top speed on the flat is 65-75 depending on wind direction and on a hill good luck getting out of third gear!!!!

Anyway I am now at the point that I suspect a fuelling issue, I have cleaned and exercised the choke, the choke bar appears to be moving normally on the carbs and there no resistance and it goes all the way home on both sides.

So suspect carb issue. my question is should I remove the carb clean what's easy to get at then put it back on and run Sea foam OR should I just run Sea foam and save the hassle of removing the carbs in the first place or something else ???

And how easy is it to get the carbs off?

Thanks in advance

Rob

 

[vinny]

Re: how easy to tremove carbs

Sounds to me like you have some torn diaphragms in the carbs. When you remove them, pull the covers off the vacuum pistons... large stamped metal covers with four Phillips head screws... and check the diaphragms. You did not mention anything about missing, backfiring, etc... Is this a new condition or has it been building for a while?

 

[formerhondaman]

Re: how easy to tremove carbs

Hi
there isn't any backfiring, it just losses power when you accelerate, like its drowning in fuel. the only way I can describe it is like riding with full choke and a bit, fuel mixture. very rich. Old plugs were Black! proper black.

I am sort of convinced that I need to take the carbs of and as a minimum remove the bit under the floats and clean it out but never worked on carbs??????.

Rob

PS this was supposed to be my reliable long commute bike 186 miles daily so I could do less miles on my bird ( now on 60 k) but so far has only made a hand full of trips in the last two months, due to this and a host of other issues, noted elsewhere. I am almost through everything tjhat could go wrong. This and the rear brake appear to be the last issues to resolve.

 

[vinny]

Rob, the vacuum pistons are easy to check... just pull the covers and gently remove the vacuum pistons and check those diaphragms...

 

[jvick98]

I have seen Seafoam clean up some carb issues, try the easiest things first.

Jim

 

[kiltman]

Have the carbs been synched?
If you're planning on doing any work on the carbs, you will have to have them synched afterwards

 

[formerhondaman]

unfortunately the history of the bike was word of mouth so I have to assume there is no history at this point and that the former owner is an idiot, not as big an idiot as me for parting with my cash but n idiot non the less.
Actions
1. I will remove the carbs and clean whatever I can get to without completely stripping them
2. I will check the diaphrams and replace if required
3 I will fit the carbs fill the tank with sea foam and give it a 186mile test run ( commute) then see if things work properly
4 report back here with the results, depends how long it takes to get the carbs off lol

and a result on my other thread looks most like its air.

Thank you to the collective here and there

Rob

 

[dwalby]

2. I will check the diaphrams and replace if required

be very careful with them, and hope they're not torn. They cost about $100 each over here, not sure about the UK, but my guess would be even more expensive.

 

[Uncle Phil]

BTW, I found it a lot easier to get the carbs out if I removed the fuel tank - which is not a big deal. It gave me more working room - not necessary but pretty easy to do - just remember the gauge wire on the left side. ;-)

 

[Bush]

Another tip - don't remove the black rubber "snorkels" sitting on top of the carbs. They can stay in place for the removal. Otherwise, they are a bit of a pain to re-install, without loosening up all the carb bodies from each other.

 

[formerhondaman]

okay sorry guys its me again. I have removed the carbs. it was actually very easy plastic and carbs off in just under 2 hours which I thought was good! I must apologies for my technical naming of bits as I have never seen a carb in real life let alone taken one to bits

so I drained the fluid from the floats bits with the screws that are on the cover, it was crystal clear.
I completely stripped out one Carbs all the brass bits and diaphragm spring covers etc basically anything that would undo I took out and they were all in absolutely fantastic condition so I left the other three alone and wiil reassemble based on the absolutely stunningly clean new like condituion. I undid the choke bar and exercised it and that was as free as a bird so Im not convinced its the choke,.
I will look at the air valve diaphrapm thing on the side tonight two screws that hols the cover on remove and look at diaphragm. however I did do up the mix screw on the carb I looked inside and it was only 1 turn or jut under fron lightly seated. spec is 1 7/8 and average from what I ve read is 2-2 1/2 turns could this be the culprit, would anyone advise at just winding them all in to lightly seated then back them out 2-1/4 turns ???? there is a drop test you can do but this is my first carb experience so trying to keep it simple.

As usual if you need further info to advise let me know or if you have advice I will be very very grateful

Rob

 

[vinny]

Honda caps off the mixture screw on carbs for a reason... shouldn't mess with them unless it's absolutely necessary. The mixture screws are very hard to access when the carbs are on the bike... and that is the only way to do the lean drop method of adjusting the mixture. It will require some special tools and some knowledge. Then you will have to sync them all (much easier than adjusting the mixture).
Before putting the carbs back on the bike, take the covers off the vacuum pistons and check the other three diaphragms. The vacuum fuel shut off valve (I will look at the air valve diaphrapm thing on the side tonight two screws that hols the cover on remove and look at diaphragm.) doesn't sound like it's an issue.
Good luck with the repairs!

 

[formerhondaman]

So if the carbs are not synched could that cause it to run Very rich?

 

[ak85lp]

It could be. Mine were out a little bit and I always had buddies following me saying the bike had a rich smell. Once I synched the carbs the mileage went from 52 mpg (Imperial) to just under 60 (59 point something). The same buddy says the rich smell was not as noticeable.

 

[formerhondaman]

Okay thanks guys, Ill check other diaphragms refit carbs and do a carb synch.
I was getting 140miles to a full tank? its a new bike to me but would expect at least 225 or more cruising on the motorway, that's more than rich which lead me think the carbs had issues.

 

[kiltman]

Check the boots for any sign of cracking.
Once you have it back together, check the valve clearances. They're more than likely spot on, however, for piece of mind, go for it, then you are probably good for another 60K

 

[formerhondaman]

Check the boots for any sign of cracking.
Once you have it back together, check the valve clearances. They're more than likely spot on, however, for piece of mind, go for it, then you are probably good for another 60K

another 60k if i get more than 140 per tank lol

 

[kiltman]

Mileage on a commute is a difficult thing to gauge IMHO. If I just do short trips in town I'm lucky to get 300km on a tank. These bikes are heavy and it takes energy to get them going. On the highway I will get 53MPG (imperial), but if there's an in town component that will drop to 40mpg and as low as 35mpg. That's what I experience. YMMV
cheers

 

[formerhondaman]

Okay here's another update the carbs are all clean, and reassembled on the bench, not convinced it was purely the carbs now as all jets needles and diphrams where very clean and in fantastic condition so decided to check the ht coil with a resistance test on the blue/yellow and black/white 3 pin connector for cylinder 1 and 3 while carbs where out and gave access
My book says the upper range is 3.19ohms I'm reading 3.8 ohms across the 3 pin connector. would this tiny difference really matter? book says outside range replace! but we are only talking .6 of an ohm and another ?100???????
Also could the ignition coil cause poor fuelling if .6 ohms really did matter or have I found another problem????? OMG wheres miss marple when you neeed her.

 

[dwalby]

My book says the upper range is 3.19ohms I'm reading 3.8 ohms across the 3 pin connector. would this tiny difference really matter? book says outside range replace! but we are only talking .6 of an ohm and another ?100???????

hold your leads together and see what the resistance of the leads themselves measure, it could be 0.5-0.6 ohm or so depending on how clean your probe tips are. If your probes aren't clean that can add a few tenths easily. Get them down to 0.1-0.2 ohms and make sure the coil connectors are equally clean, and do the measurement again. I can't say 100% that you don't have a weak coil, but I'd hold off on buying a replacement until you can do further diagnosing.