XJ650 vacuum leak... do i need new carb boots?

My XJ650 has a vacuum leak sourced at the carb boots... the thing is, the boots seem to be in great shape, supple rubber and no cracks on any of them.

They just seem too "short" and I don't know if the previous owner jury-rigged some boots from something else onto this bike, or if they're supposed to be like this, but no matter what I can't get a seal using the metal bands over the boots(metal bands that you tighten the screw to tighten... sorry name is escaping me right now).

any tips? i'll post pictures tomorrow if i need to. it's as if the boots need an extra .5 inch to fit properly, seated in the airbox and over the carb inlet.

i know rubber will shrink over time, but like i said, they're supple and seem fairly new.

 

It is very possible that the previous owner replaced the boots and did not get the rack seated properly.

The carb joint boots have a ridge molded into them that seats into the groove on the carb neck. This can sometimes be a pain to get the carbs to seat properly. Check to make sure that the carb rack is seated completely into the boots.

Try using a light coating of oil inside the boot lip to help it slide past this ridge. The boots should be seated nearly flush with the carb body.

I have heard of guys using ratchet straps to help pull the rack into place, or even boards to push the carbs in. Either way you will have to wiggle the rack up, and down. or side to side to get them in.

Hope this helps
Ghost

 

Whoa up there; WHICH boots?

I think MiGhost is talking intake manifolds (carb-to-motor) and you seem to be referring to the airbox to carb boots.

The airbox-to-carb boots DO SHRINK; sometimes worse than others. Once they shrink badly enough, replacement becomes the only option. Luckily they're not all that expensive, especially compared to the intake manifolds.

That being said: are you aware that the airbox has mounts allowing it to move fore and aft in the bike once the mounting screws are loosened; is it possible that your airbox is "tightened down" in a rearward position?

Something else that works, implausible as it seems, to restore the boots to closer their original dimension is to BOIL them. Drop them in rapidly boiling water; let them boil away for about 3~5 minutes, then remove from heat and let them sit in the hot water until it cools down enough you can handle them.

 

cool guys, to be clear i am referring to the airbox-to-carb boots. i will have to check the position of the airbox, as it seems to be sucked down pretty tight. if not i'll boil them.

 

Could be a matter of them getting mixed-up, ... if they were pulled-out.

Here's what I do.
Pull the four Boots.
Line them up, level.
Look for 2 that are "Straight"
Other-2; slightly tilted.
The tilted ones are 1 & 4.

While they are out, wrap a sheet of sandpaper around a 5" section of closet rod.
Sand the Airbox openings, ... just a tiny-bit larger. Just enough to make rotating the Boot a bit easier.
Sand the Locking Channel of the Boots; too.
Finish them with all with 1200.

Shoot some Heavy Duty Silicone Spray into a Tuna Can.
Paint the Airbox Holes and Boot Locking Channels.

Loosen the Airbox fasteners.

Reinstall the Boots.
Get them over the Intake Horns and clamped-down.
Tighten the Box.

 

Thanks for the great run-down. I understand all of it except for when you say "wrap a sheet of sandpaper around a 5" section of closet rod."

can you put that in laymen's terms please? What is the closet rod?

 

Closet Rod - PVC Pipe
A Cylindrical Object.

Wrapping Sand Paper around a cylindrical object allows you to sand curved surfaces.

Wrap sand paper around a short cylindrical object and increase the Inside Diameter of the Airbox Boot Holes very slightly.

The idea it to be able to rotate the Boot without a fight.

Having some tools helps, ... too.

http://www.electricaladvantage.net/pick ... cekit.aspx

 

oh wow... i guess i was thinking too technically thanks for the information it's very helpful!

 

Check what Fitz and Rick said about moving the airbox back,I just did that this morning to reinstall my carbs.That 1/2 inch makes all the difference!

 

problem solved guys, the issues were: the inner boots were swapped with where the outter boots were (ie, i had to move the inners to the ouside and the outters to the inside). also the airbox was mounted as far back as possible for some reason. i mounted it all the way forward and the bike runs fine now.

another issue is still there though, which i thought this would fix: the bike wont idle unless fully choked, and there's a whistling/squealing sound coming from the top end (sounds like the carbs, but i can't really tell specifically).

before i just fixed the boots, the bike wouldn't start or idle unless fully choked and the petcock switched to prime. now it will start with the petcock in the on position, but still, as i said before, wont idle without full choke. any ideas?

 

A Bike that won't Idle unless fully "Choked" means you have to check a few things.

1. Correct placement of AIR Jets:


2. Correct Size of Pilot FUEL Jets.
3. JETS are Clean and pass fuel.
4. Passages are Flushed and Clean.
5. Bench Sync done with Throttles virtually closed. (3X5 Card or Strips of Resume' Paper as Feeler for setting Bench Sync.)
6. Mixture Screws Operational.
7. Mixture Screws correctly installed: O-ring < Flat < Spring < Screw Body||

Won't run without Choke = Fuel needed = Lean = Add some richness.

 

great thank you again! I found the Haynes Service/Shop Manual for this bike (I'm sure most of you already found it... but here's a link to the one I got: http://www.4shared.com/get/M1hpX3QZ/Yam ... nes_M.html )

It's nice high definition PDF format. Definitely helpful as well!

 

and yes, you have to wait like 2 minutes to download it, but it's free, so whatever.

 

ANy chance someone would have a working link of high PDF of Haynes, i did buy an online version but the quality is mediocre.