KZ 750 E carb overflow trouble

Hello again, back in May my son fitted a Dynojet kit and pod filters to his 81 KZ 750. The result (chronicled in this forum) was gas running from the overflow on at least one carb. I fitted new 5/32 gas line over the leaky brass tubes in the float bowls while he carefully cleaned the needle seats. When re-assembled all was well for a short time ,then the spillage began again. Our guess is that contamination from the dirty tank keeps foiling our efforts. Repeatedly. So the tank is off as we try to remove what's left of a failed attempt by the previous owner to Kreem the tank.It's got a bunch of Zip Strip in there now. Has anyone out there dealt with this before? Any suggestions and / or offers to sell us a decent used tank are greatly appreciated.

dimestorehero wrote: Hello again, back in May my son fitted a Dynojet kit and pod filters to his 81 KZ 750. The result (chronicled in this forum) was gas running from the overflow on at least one carb. I fitted new 5/32 gas line over the leaky brass tubes in the float bowls while he carefully cleaned the needle seats. When re-assembled all was well for a short time ,then the spillage began again. Our guess is that contamination from the dirty tank keeps foiling our efforts. Repeatedly. So the tank is off as we try to remove what's left of a failed attempt by the previous owner to Kreem the tank.It's got a bunch of Zip Strip in there now. Has anyone out there dealt with this before? Any suggestions and / or offers to sell us a decent used tank are greatly appreciated.

Acetone will remove the Kreen coating.

Where fuel discharge from overflow isn't caused by imperfect float valve or float function, it may result from a cracked overflow tube.
May bench test by removing the float bowl, fill it to top of the overflow tube, and watch for continuing discharge where fuel level is below top of the overflow tube.
If overflow tube isn't cracked (or leaking where it connects to the float bowl) fuel discharge should stop when fuel level doesn't exceed height of the tube.

May use common rubbing alcohol for this testing because it doesn't smell so bad.

Good Fortune!

Thank you for taking time to make some good suggestions. Our overflow tubes are cracked hence the small diameter (5/32 I believe)gas line slid down over them. It's a trick way to seal them picked up from a local tech that has worked well. The overflow has also come from different carbs at varying times leading me to suspect continuing re-contamination. One other clue is that we installed a petcock re-build kit that initially cured the problem ,but after a period of running will no longer stop the flow in the ON position. Subsequent cleaning of the petcock produces temporary proper action only to return to an inability to stop gas from dumping all over the floor. Once the tank is cleaned do you think we should Caswell coat the inside or leave it and be carefull in the future that it doesn't corrode again? Thanks again.

dimestorehero wrote: ...overflow tubes are cracked hence the small diameter (5/32 I believe)gas line slid down over them. It's a trick way to seal them picked up from a local tech that has worked well. The overflow has also come from different carbs at varying times leading me to suspect continuing re-contamination. One other clue is that we installed a petcock re-build kit that initially cured the problem, but after a period of running will no longer stop the flow in the ON position. Subsequent cleaning of the petcock produces temporary proper action only to return to an inability to stop gas from dumping all over the floor. Once the tank is cleaned do you think we should Caswell coat the inside or leave it and be carefull in the future that it doesn't corrode again?....

Snugly fitted tube section may indeed sometimes serve to prevent fuel from leaking through a crack in the overflow tube.
Possible remedies also include solder, JBWeld, heat-shrink tape, and perhaps others.

Another common overflow failure is a clogged overflow circuit. Where it may be difficult to clean the small holes/passages in the float bowl.

Imo, interior fuel tank coating is eventually doomed to failure, and would restrict its use to sealing pin-holes in an otherwise non-repairable leaking fuel tank.

If not already fitted, an accessory aftermarket in-line fuel filter should imo always be used on these bikes, even with a perfect as-new fuel tank interior. Not only to intercept crud from the inside of an imperfectly clean fuel tank, but also to help filter the fresh new crummy gasoline from each re-fill.

In-line filters are relatively inexpensive and readily available at bike shops, Z1 Enterprise, etc.



Click > www.z1enterprises.com/detail.aspx?ID=293

Absent an in-line fuel filter, many a freshly cleaned pristine set of carbs has been instantly re-contaminated by the first flow of incoming fuel.

Even a perfect as-new petcock is woefully insufficient. It serves more as a strainer for larger particles and grit, which is inefficient compared to an in-line filter.

There are several good methods for returning the fuel tank interior to as-new condition. And many good threads here on KZr about the subject.

Keeping the tank filled helps avoid new rusting, but long term storage is another matter involving other considerations.

Bottom line -- flush the tank (refurbish interior as needed); clean the petcock (again); install an in-line filter.

Good Fortune!