Carb Adjustments

[dkaiser]

Hello All,

 

Let me run this by you, and I will try to keep it short.

 

I bought this '87 as a fixer upper. Right away I saw that I needed Carb Diaphrams -- wow over $200. I found what was supposed to be a rebuilt carb on ebay for $200. I asked if it had new Diaphrams, Needles and Seats, he said it did, so how could I go wrong. Got it and put it on -- had to turn the idle screws out 5 turns to get it to run. Decided my old carb was probly better, so today I put the diaphrams, needles and seats in my old carb after taking it apart and soaking it in Sea Foam for 4 days.

 

It started like a champ. With the Filter and airbox cover off it rips. (This is all on the center stand) when I put the cover on it dogs out at about 4500 RPM --- air starved, me thinks.

 

Just a note, I have not synced yet.

 

I saw some talk on here about drilling th airbox and some hopping up procedures, could some of my parts be needing the airbox drilled or...

 

Any observations are welcome.

 

Thanks

 

D

[Cutty]

Before you drill your box, take a small rubber hose tape it to the top of box leaving a small gap and than road test. Main jets and emulsion tubes are they clean??

[CrazyHorse]

5 turns seems like a big amount. These bikes usually dog out if the cover is off. Almost sounds like too much fuel.

[GeorgeS]

The Idle adjust needle jets, Correct setting, is bottom them out ( carfully not to damage needles ) and open them 2 1/4 to 2 1/8 turn CCW. ( this is the agreed upon correct setting, info is NOT in the Service Manual )

 

The Three, Sync screws, when you get a sync tool hooked up, should adjust ( balance out ) on all three of them with no more then 1/4 turn on any one screw, unless sombody really messed them up.

 

Best to do a Sync, and go from there. These engines run bad, if the Mechanical Linkage's are not in Sync.

 

Leave the Air Box, in Stock configuration untill you get it running right.

 

Also a note: $200 for the carb diaphrams is a bargain, they retail for about $120 list price. Remember these rubber diaphrams are almost 20 years old on you bike !!

Rubber, don't last forever.

[dkaiser]

Sorry I was not clear, 5 turns out was the other carb, this one is starting real good at 2.5 turns

[dkaiser]

Before you drill your box, take a small rubber hose tape it to the top of box leaving a small gap and than road test. Main jets and emulsion tubes are they clean??

 

Main jets are new and pristine. Emulsion tubes, not sure what they are?

 

D

[dkaiser]

The Idle adjust needle jets, Correct setting, is bottom them out ( carfully not to damage needles ) and open them 2 1/4 to 2 1/8 turn CCW. ( this is the agreed upon correct setting, info is NOT in the Service Manual )

 

The Three, Sync screws, when you get a sync tool hooked up, should adjust ( balance out ) on all three of them with no more then 1/4 turn on any one screw, unless sombody really messed them up.

 

Best to do a Sync, and go from there. These engines run bad, if the Mechanical Linkage's are not in Sync.

 

Leave the Air Box, in Stock configuration untill you get it running right.

 

Also a note: $200 for the carb diaphrams is a bargain, they retail for about $120 list price. Remember these rubber diaphrams are almost 20 years old on you bike !!

Rubber, don't last forever.

 

OK, on this set of carbs I have them turned out 2.5 turns, and it started right up. I will turn them in a quarter or so and see what that does

 

D

[dkaiser]

5 turns seems like a big amount. These bikes usually dog out if the cover is off. Almost sounds like too much fuel.

 

 

Sorry for the confusion. 5 turns was on the other carbs, this one I did 2.5 turns.

 

It is dogging out when the cover is on. Screams with the cover off.

 

D

[Gearhead]

Emulsion tube is also called a needle jet. It is the tube with holes in the side that drops in from the carb throat and the main jet screws into it from the bottom. The needle rides inside it.

 

That is odd behavior, the airbox thing. When everything is correct it is opposite - screams with airbox on, dogs with it off. Very sensitive to having the airbox in place. Significant mods to the airbox, or individual filters or whatever, must require significant rejetting.

 

Regarding airbox mods, I originally thought that drilling (4) 1/2" holes in my lid bumped my mileage up from about 35 to about 38. I have several tanks worth of data that show this, so something bumped my mileage, but now I can't get over 33-34 and I have tried taping over the holes and leaving them open with no change. Still haven't figured that out. BOTTOM LINE: don't mod the airbox to fix your problem. This bike will run well stock - get it that way. THEN - if you have the modifying itch that I can't seem to escape - you can play around with that kind of stuff.

 

Jeremy

[mbrood]

Dave,

 

Although it looks straight forward... you wrote...

"I put the diaphragms, needles and seats in my old carb"...

 

Are you SURE the needles and jets were the SAME as your stock ones?

Guys can rejet their carbs for various reasons and this might be the case?

[CrazyHorse]

Are you SURE the needles and jets were the SAME as your stock ones?

Guys can rejet their carbs for various reasons and this might be the case?

I was thinking same thing.

[dkaiser]

Dave,

 

Although it looks straight forward... you wrote...

"I put the diaphragms, needles and seats in my old carb"...

 

Are you SURE the needles and jets were the SAME as your stock ones?

Guys can rejet their carbs for various reasons and this might be the case?

 

 

 

Hi mbrood,

 

No, I am not sure. I bought a "rebuilt" Carb off of Ebay. When I put it on the bike, it was not right, had to turn the idle needles out 5+ turns to get to run, and it ran crappy. So I took my old one apart, cleaned it, soaked in Sea Foam for 4 days, and reassembled with the Seats, Needles and Diaphrams from the new one (I was told they were new, and they did look much better).

 

An observation -- the needles that I m running now have a sharper point on them than the old ones.

 

I went out and played with it a little now, If I have it at about 4500 with the air box cover on, and crack the air cover open a quarter inch, RPM's climb a seems to run nice. I think I may put some spacers in the cover and play around with that. If it is rejetted, it could need more air? makes sense to me.

 

I will get a Carb Sync tool and start on syncing it too.

 

D:)

[Condor]

Just a question on the Ebay carbs. Did the engine run bad when the cover was off or on??? If it ran bad with the cover off, that's more like normal on these engines....

[dkaiser]

Just a question on the Ebay carbs. Did the engine run bad when the cover was off or on??? If it ran bad with the cover off, that's more like normal on these engines....

 

 

Both, it just ran crappy, I don't really think it was really rebuilt. I think he put new diaphrams, needles and seats in, and cleaned up the outside. what makes me think that is that, is that I had to turn the idle needles out at least 5 turns just to get it to run. At that is was cracking and popping alot, a lean fuel air mix. I think.

 

The main problem with my original carbs was holes in the diaphrams, I tried patching them, as per another thread on this board, then it ran well till the patches let go. As usual, it ran better with the air box cover on, when I had the patches on.

 

The difference must be the needles and seats.

 

D

[rhncue]

Sorry for the confusion. 5 turns was on the other carbs, this one I did 2.5 turns.

 

It is dogging out when the cover is on. Screams with the cover off.

 

D

 

Sounds to me as if you are running extremely rich. I doubt if it is even jets but probably float levels set way to high. If the bike will scream with the cover off the air box it has to be getting an awful lot of gas.

 

Dick

[dkaiser]

Sounds to me as if you are running extremely rich. I doubt if it is even jets but probably float levels set way to high. If the bike will scream with the cover off the air box it has to be getting an awful lot of gas.

 

Dick

 

 

Well, with the old Diaphrams, Needles and Seats in it ran great with the cover on. I did not mess with the floats. The only thing different is that it is clean, new needles, seats and diaphrams. Other than that it is my old carb. I am leaning toward that these are rejetted HP?

 

It idles nice and really sounds good, with the cover off or on considering I have not synced yet. Just when I open it up that is when I see the difference.

 

D

[dkaiser]

Hi All,

 

I just got done syncing the carbs with the homemade carb sync tool described on this board. Worked pretty well, number 3 was way out. She purrs now.

 

So I took it up the rode. Mushed out at about 5 grand, so I took off the top of the airbox and strapped it to the back of the bike, WOW! she screams!

 

Never heard it run so good, I think that those must be some performance jets?

 

I am thinking I may play with opening up the airbox in some way that may be adjustable, a louver or something?

 

D

[mbrood]

There's quite a few of us that would REALLY like to know what jets and needles you put in there! If we could get rid of that big box and just use some individual filters it might be just great! I think there's another of our members that was wanting to go that route.

 

It's always a designed system... certain jets and needles matching the designed housing vacuum,, cam dwell and exhaust setup is the "magic" setup.

 

Guys go through extensive dyno tests to find a "magic" spot with performance changes. NOT cheap... and YOU may have stumbled on a new performance trick!

 

I'd be REAL interested in your current mileage numbers WITH the cover off...

(It's easy to get high performance if you will take a 10 mpg hit.)

[Guest hotrod355]

My 89 did the same thing...I drilled the airbox cover....that helped ...But when i put some stright pipes on it ...IT SCREAMS now...if you like it loud.