Leaky carb boot

I have a leaky carb boot. Determined this by spraying carb cleaner around it and heard an RPM increase at idle. There are not any cracks that I can see visually, but I have not pulled the boots of the bike yet. Are there any fixes that do not require buying / installing a new one or is it best just to get a new one?

There are no real fixes for those old brittle carb boots.
If the carb boots have porous areas buy it new, they will last for the next 10 years.

Scirocco is correct; replace the carb holders. Over time they develop tiny cracks on the mating surfaces that cannot be seen with the carb holders mounted on the engine. Those tiny cracks may look like they are insignificant, but they really do let air enter the system when the throttle is closed or nearly closed. Folks have tried to seal them with all sorts of home remedies, but those remedies are only temporary at best. Replacing the carb holders with new ones is the only way to really correct the problem. Ed

When I install carb boots I apply a little gasket sealer to the boot surface.

Thanks everyone - I'll purchase some new carb boots (sounds like it is necessary). One other question - I'm like 80% sure the leak is just in the right boot but should I just go ahead and replace both? Z1 Enterprises sells them two at a time.

Thanks again!

Replace both. If one is leaking a fair amount the other is leaking at least a little or soon will be. Ed

Both it is. Thanks again!

Suggest you apply the thread penetrant of your choice (Liquid Wrench, Kroil, etc.) to the threaded fasteners holding the boots to the head now, so they can be soaking for a good long time. Repeat every couple of days.

If any of the screw holes in the head are open at the back (not blind holes), get some penetrant in those open passages too, as the greenish corrosion will likely have developed there also. That corrosion can act like a very effective thread-locker.

If the screws are cross heads, use quality JIS screwdrivers or JIS bits in an impact tool to remove them.


Good Ridin'
slmjim & Z1BEBE

In addition to the penetrant I would tap tap tap the screws w wood block & mallet. the vibration should help to free up those fasteners which can be difficult to remove. don't pound the fasteners & do not use a sledge hammer.



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martin and slm:

The thread on the carb holder fasteners are obstructed by the existing boots so how do you get penetrant to the threads? Do you just spray it around the boots and hope it makes its way in?

By tapping with wood / mallet, do you mean place the wood on the screws and then tap (i.e. tap the wood to push the screws further down into the hole)? I'd assume hitting them from the side could shear off the bolts and would not be good.

You mention the back of the screw holes (in the engine head) may be open and can be sprayed with penetrant -- how does one get to those holes to see if they are in fact open? Is there a way to get to them easily without removing the engine from the chassis? I don't have a lot of space to work with.

Also, I checked the service manual and did not see any info on recommended torque for the carb holder fasteners. So I'm guessing add a non-perm locking agent and tighten them firmly but not enough to break/strip the bolts?

Thanks.

I think the threads are 6M fine. If you have JIS screws you should hand tighten and can use a little blue thread lock, although it's not mentioned in the manual. If you have bolts or allen screws you should tighten to 70 to 80 inch lbs and also use a little blue thread lock. Any more torque and you risk stripping the threads in the manifold. Note that I said INCH lbs, not ft lbs.

About all you can do is apply penetrant around the screw heads. It may or may not work it's way into the underlying threads.

What 650ED means is, to tap the head of the screw on-axis. Inserting a screwdriver tip into the head and rapping the handle on it's end like a punch. will accomplish the same thing.

The top screws for the carb boots on a Z1 are in blind holes. The bottom screw holes for Z1 carb boots extend all the way through the boss on the head. That opens the bottom holes opposite the screw head to atmosphere. We've seen those screws corroded into the holes so thoroughly from moisture entering the opening in the boss that the screw head twists off before the screw shaft begins to turn, because the shaft is locked into place from corrosion at the open end of the hole. We only mention it to maybe save you some grief. We're not that familiar with 440 heads.

If you examine the head in the areas where the boot screws enter their boss, you should be able to determine if any of the screw holes pass through their boss. If all the holes are blind you can only treat the screw head areas & hope for the best.


Good Ridin'
slmjim & Z1BEBE