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Discussion Starter · #1 · (Edited)
Howdy all,

I got a 2000 TBS with 25,000 miles this summer in July, and had been very happily riding until the beginning of November when one day riding down the hill I live on for my daily commute, my engine dies, and every time I started it up it would hold an idle for a little while, but very inconsistently and then it would die. Took it to the shop and apparently the issue is my carburater, it's leaking fuel into my airbox, so I have my carburater rebuilt and get some new spark plugs. Now when I got it back from the shop the RPM's were set way too high, somewhere like 1500-1600, and after setting it back down to just above 1000, it has a similar issue to what was happening before it went into the shop, albiet to a lesser degree. Video is of what happens now, as another note rpm's are steady but a bit hesitant just after starting up, and once warmed up it get's worse and an idle won't hold for more than 20 seconds before shutting off. Also on my farthest right carb the drain screw on the bottom won't go in all the way, it's not leaking, but it looks off? I'm wondering if it could be causing a loss of pressure or something.


In the video I'm holding the throttle steady and changing around at roughly 500rpm incriments, you can see how jumpy it is when opening the throttle and how at idle it'll shut off.

Any and all help is very much appreciated, thanks.
 

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Discussion Starter · #3 ·
If I were a betting man, I'd bet you have a vacuum leak somewhere.

The rubber manifolds between the carbs and heads?
Or the rubber caps on the ports that are used to connect manometer when balancing the carbs?

BUT I never bet on anything!
Hmm certainly a possibility, the rubber is a bit cracked. Thanks for the input, I'll get a better look tomorrow, these are some older pics.
 

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Looking at those photos I would start with the carb rubbers and replace them.
 

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Try tugging on the carbs or poking at that crack to see if anything changes. Another trick is to spray a little carb cleaner on the crack. If it gets sucked in and burned the engine should rev up momentarily.
 

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It's a vacuum leak, and it is those cracked rubber boots and the plugs.
My CBR900rr idled exactly like that; the boots weren't cracked though, but were solid and non flexible, so it was not sealing properly.
Replace those, nice and smooth.
 

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Discussion Starter · #9 ·
Who was the shop you took it to? They "rebuilt" the carburetor? Remind me to avoid them.
The shop was Desmoto Sport in San Francisco. Here's a chopped up invoice for the job, yeah you and me both, I'm never going there again. They quoted me $500 too.

P.S. Think I could just spray some Flex Seal™ up in there and save money?
 

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Yeah, assuming you took those photos after the repair, those vacuum caps don't look so new, like the invoice says. I know those guys; they have (had) a good reputation, but it looks like you got hosed.

Speaking of hoses:

If your bike is a California-spec bike (likely), you've got alot of extra emissions plumbing hanging off the carburetors. Most of the hoses are almost certainly shot. Three of them are quite important: the 2 carb vent hoses that go to 2 solenoids (one each) and a hose to the evaporative canister. If either of the vent hoses are blocked (or the solenoids don't open), your carbs will flood. In other words, those vent hoses must be open to the atmosphere during running. (The solendoids close during stop to keep the fumes from escaping).

The hose from one of the vacuum ports to the evap canister could be leaking air which would cause a problem. Or the canister could be shot.

I recommend you junk the whole system, but if you want to stay legal and do the right thing environmentally, replace at least the hoses and examine the associated joints, ells, tees, and valves.

Good luck!
 

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Discussion Starter · #12 ·
Well, it looks like they gave you a good deal on the vacuum caps... ;)
Ahh ha, yeah the photos I put up were older, those caps were a mess :eek:

New ones are all in order, but the other seals are pretty badly cracked on my left carb and my right's not looking too hot either. Time to go about getting some carb cleaner to test, might just replace them anyways because I'm sure they'd be a problem soon enough.
 

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Discussion Starter · #14 ·
Yeah, assuming you took those photos after the repair, those vacuum caps don't look so new, like the invoice says. I know those guys; they have (had) a good reputation, but it looks like you got hosed.

Speaking of hoses:

If your bike is a California-spec bike (likely), you've got alot of extra emissions plumbing hanging off the carburetors. Most of the hoses are almost certainly shot. Three of them are quite important: the 2 carb vent hoses that go to 2 solenoids (one each) and a hose to the evaporative canister. If either of the vent hoses are blocked (or the solenoids don't open), your carbs will flood. In other words, those vent hoses must be open to the atmosphere during running. (The solendoids close during stop to keep the fumes from escaping).

The hose from one of the vacuum ports to the evap canister could be leaking air which would cause a problem. Or the canister could be shot.

I recommend you junk the whole system, but if you want to stay legal and do the right thing environmentally, replace at least the hoses and examine the associated joints, ells, tees, and valves.

Good luck!
Ahh thanks for the tip, it's most certainly California spec'd, I'll take a look at the hoses and may just end up junking the system, don't tell any local P.D. though ;P
 

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Discussion Starter · #15 ·
Got a great deal on rubbers from someone on ebay who ordered the wrong trio and now I'm hopefully going to be able to start riding again soon :D One last thing, does anybody know if I need to take out my carbs completely or if I could manage replacement by just slotting the rubbers in and out?
 

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It will be much easier on you to pull the carbs out to install the carb boots. You will not need to completely remove them, just slide them out one side.
 

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Do not make the normal mistake of attempting to remove the throttle cable at the carbs! If you decide to fully remove the carbs, take the cable loose at the handlebar/control. If you do not fully remove the carbs, the cable can stay connected. It is possible to fit new rubbers without the carbs all the way out, but you'll need 3 extra-slender hands with 6 fingers each.
 

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Get one of those little pouches of bulb grease that they sell at the counter of every auto parts store, and rub a very thin film of the stuff around the inside circumference of each boot that connects to the rear of the carb from the airbox side. These can be a bitch to slide over the carbs, and that little bit of lube can really make a huge difference. If you have a swimming pool, that silicone grease that you use for the orings is the same stuff.


PS - If they had used a little of this on you at the dealer, it wouldn't have hurt so much either:surprise:
 

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Discussion Starter · #19 ·
Well, here is an update to my issues, unfortunately they have not gone away :/

After replacing my rubber manifolds I found out that, while old and decrepit, they had not actually cracked through, the worst part wasn't even halfway cracked through. I also changed the oil out because it was overfilled and the previous owner lied about when the last oil change, stuff was black as the night.

However my problem with my rpms below 3k has not gone away, it's actually gotten worse. Now with my choke opened up above 3k, there are no problems, but using my throttle the problem persists even above 3k. Also the jumping is more erratic and happens more often.

Here's a video showing what I'm talking about, the first clip is with the choke open, the second is with the throttle and no choke.

https://youtu.be/nMimrKcRd9Y

Any clue what I might be dealing with if it's not a vacuum leak? Maybe it still is?
 

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Discussion Starter · #20 ·
Do not make the normal mistake of attempting to remove the throttle cable at the carbs! If you decide to fully remove the carbs, take the cable loose at the handlebar/control. If you do not fully remove the carbs, the cable can stay connected. It is possible to fit new rubbers without the carbs all the way out, but you'll need 3 extra-slender hands with 6 fingers each.
Christ you weren't kidding, everything is ezpz until you start on that center carb. No room to move around, too far in to use most normal tools(I made liberal use of wire coat hangers es extensions of my hands), and if you accidentally drop a screw have fun fishing it back out for 15 minutes. Still 100x better than spending $$ in the shop though.
 
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