Topic: 25mpg but runs GREAT....now 33mpg!!!

[S-Dog]

I just went through my bike with the help of Chris(FrostyPuck).  Adn My bike is now running great... the only issue is that it only gets 25mpg.  Here is what I went through.

New plugs

cam chain adjust

cleaned out the carbs completely including jets(slow and main) running 112 and 40

bench synced then synced them with the syncie tool thingy.... getting 21mb of merc all the way across

adjusted the mix(air?) screws 1.5 out

timing looked good

adjusted the idle(900-1000 all day long with no jumping around)

It seems to run REALLY rich especially at idle.  The choke seems to have no good effect on the bike.(I can start it without the choke in 40 degree weather)

Im not sure if there is anything else I can say about it.

I tried to search around but none of the examples I found seemed to be similar to my issue.

Any help is appreciated.

Thanks,

Scott

[mlinder]

Turn out the air screws.

[OldSchool_IsCool]

Time to look outside the engine.

- sticky brake?
- tires up to pressure?
- chain/sprockets in good shape?
- stock ratio sprockets?
- too many trips to the buffet? (my personal issue)
- no gas leaks?
- good tire alignment?
- dragging an anker or sail (cargo issues)?
- wheels spinning freely (tight/worn barrings)
- chain properly tensioned?

[UnCrash]

- dragging an anker or sail (cargo issues)?

He just might be!

That bike sounds more like a boat without the baffles! 

[scondon]

  I didn't see "valves gapped" in your list of things done. You'd want to do this before synching the carbs. Also, please verify what you mean by "timing looks good". What clip position are your jet needles in?

   ignition timing and carb tuning can make mpg vary by 10mpg, or so, depending on how accurately it is done. This is in addition to what others have already posted.

[OldSchool_IsCool]

It seems to run REALLY rich especially at idle.  The choke seems to have no good effect on the bike.(I can start it without the choke in 40 degree weather)

Once warmed, does the engine respond to ANY change with choke?  Could it be that the choke is broke and is always closed?  That would definitly cause a rich condition.

Crash said it sounds like a boat.  Are there baffles in your mufflers?  Maybe your exhaust doesn't allow your engine to brethe properly.

Floats adjusted properly? 

[S-Dog]

floats are adjusted
valves gapped before sync.
no baffles in exhaust(stock exhaust)
stock gearing
rolls perfect
chain is tensioned right
no gas leaks... all brand new lines
I am 260lb so the buffet issue could be there...

when I give it choke it just dies out.... also at idle I can smell gas

Before I went through the carbs they had been "rebuilt" (kinda) by a crappy, horrible mechanic.  all 4 sync screw lock nutes were gone , cyl 2,3 and 4 were adjusted where the carb sync nut was flush with the top of the screw(no place for a lock nut and they were superglued(YIPPEE)) carb 1 was 1/3of the way down the screw but did not adjust. it acted like it was stripped.... the float were all over the place... I am guessing because of the carb sync nuts.

He did a horrible job.  Even with all those problems I got 38mpg. Chris and I went through the carbs replacing the missing and broken stuff and syncing them up nice like.

I will try the air screw.... I think that is for low end too...right? might be the ticket.

[mlinder]

floats are adjusted
valves gapped before sync.
no baffles in exhaust(stock exhaust)
stock gearing
rolls perfect
chain is tensioned right
no gas leaks... all brand new lines
I am 260lb so the buffet issue could be there...

when I give it choke it just dies out.... also at idle I can smell gas

Before I went through the carbs they had been "rebuilt" (kinda) by a crappy, horrible mechanic.  all 4 sync screw lock nutes were gone , cyl 2,3 and 4 were adjusted where the carb sync nut was flush with the top of the screw(no place for a lock nut and they were superglued(YIPPEE)) carb 1 was 1/3of the way down the screw but did not adjust. it acted like it was stripped.... the float were all over the place... I am guessing because of the carb sync nuts.

He did a horrible job.  Even with all those problems I got 38mpg. Chris and I went through the carbs replacing the missing and broken stuff and syncing them up nice like.

I will try the air screw.... I think that is for low end too...right? might be the ticket.

While the air screw will affect all throttle positions, it's effect lessens as the throttle opens.
So yes, it does affect, primarily, the idle to 1/8 throttle position.
How many turns out are they now?

[BobbyR]

For what is worth I was a bit overzealous in cleaning my slow jets and opened the main orifice quite a bit. Bike stated without the choke and I was blowing raw gas out of the pipes. You may also be flooding.

[S-Dog]

the air screw is out about 1.5 turns...

[mlinder]

I don't know these carbs. Is the air screw on the filter or head side?
If it's on the filter side, try 2 turns out. Opposite if on the head side.
(oh yeah, make sure none of your jets vibrated out and are sitting at the bottom of the bowl. No, don't ask.)

[S-Dog]

filter side..... I will try it when I get out of work... I have a 700 mile trip tomorrow so 10mpg will save me a bit of cake.

[paulages]

are you sure it's not supposed to be 1 turn out on the K5?

[mlinder]

That would make it richer.
You'd think he'd need that, with no baffles, but hey..
Are you running stock airbox, or what?

[UnCrash]

That would make it richer.
You'd think he'd need that, with no baffles, but hey..
Are you running stock airbox, or what?

Yep, he's running the stock airbox.   I'm not sure about the status of the filter though...

[paulages]

according to the tech section on this site the K5-6 should be 1 1/8 turns out.

[mlinder]

He should check his filter. Clogged filter will cause rich condition.

Paul, he's got open baffles, which as you know, changes the carb tuning.
Mine are out only 7/8 right now, and I need to go up to 50's on the idle circuit.
Off topic, looks like it's gonna rain all weekend, but lets keep an eye on the weather, for a ride, eh?

[S-Dog]

I have stock everything.... just no baffles... seemed that people back when liked it like that... as a side note I turned the screws 1/2 out(I think the total is 2 now) and its running better... the choke is starting to work like it should.... should I yank the air filter and see how it acts?
I am guessing that would make it leaner in an extreme way.....

[Bodain]

floats are adjusted

when I give it choke it just dies out.... also at idle I can smell gas

When you give a warm engine choke and it dies. Thats a good thing. It means the choke is working. If your smelling gas while the bike is sitting and idling. Look on the ground under the bike. Is it dumping gas from the overflow tubes. Gas on the ground doesn't lead to good MPG...

[mlinder]

I have stock everything.... just no baffles... seemed that people back when liked it like that... as a side note I turned the screws 1/2 out(I think the total is 2 now) and its running better... the choke is starting to work like it should.... should I yank the air filter and see how it acts?
I am guessing that would make it leaner in an extreme way.....

If it's running better a half a turn more out, then yeah, it's running rich, for some reason.
Can't explain that issue, considering you are running open pipes.
Please check the filter again, make sure it is clean, and no blockages. Did you do something like spray the filter with filter oil? Far as I know, stock filters are not supposed to be oiled. Would also cause rich condition.

[HondaMan]

I just went through my bike with the help of Chris(FrostyPuck).  Adn My bike is now running great... the only issue is that it only gets 25mpg.  Here is what I went through.

New plugs

cam chain adjust

cleaned out the carbs completely including jets(slow and main) running 112 and 40

bench synced then synced them with the syncie tool thingy.... getting 21mb of merc all the way across

adjusted the mix(air?) screws 1.5 out

timing looked good

adjusted the idle(900-1000 all day long with no jumping around)

It seems to run REALLY rich especially at idle.  The choke seems to have no good effect on the bike.(I can start it without the choke in 40 degree weather)

Im not sure if there is anything else I can say about it.

I tried to search around but none of the examples I found seemed to be similar to my issue.

Any help is appreciated.

Thanks,

Scott

Um...what bike is it? 

[Gordon]

Um...what bike is it? 

It's always something with you, isn't it?....

[paulages]

I just went through my bike with the help of Chris(FrostyPuck).  Adn My bike is now running great... the only issue is that it only gets 25mpg.  Here is what I went through.

New plugs

cam chain adjust

cleaned out the carbs completely including jets(slow and main) running 112 and 40

bench synced then synced them with the syncie tool thingy.... getting 21mb of merc all the way across

adjusted the mix(air?) screws 1.5 out

timing looked good

adjusted the idle(900-1000 all day long with no jumping around)

It seems to run REALLY rich especially at idle.  The choke seems to have no good effect on the bike.(I can start it without the choke in 40 degree weather)

Im not sure if there is anything else I can say about it.

I tried to search around but none of the examples I found seemed to be similar to my issue.

Any help is appreciated.

Thanks,

Scott

Um...what bike is it? 

i just guessed 1975 cb750K by his signature.

[HondaMan]

 
Duh.

[Jerry Rxman Griffin aka MuthaF'er]

Stock airbox. Put the 105 mains back in and see what it does. Have we discussed the needle positions? Any chance the needles and needle jets are worn and even the stock setting is too rich?! My thoughts are if it's burning too much gas it must be set too rich?!

I'm running 115's in place of my stock 105's with a kitted engine at 6800 feet 70-80 mph and getting 45mpg. Luck?! Hondaman, have I said thanks for the 115's. It's screaming past 6000rpm.