Checking needle and seats for leaks

I was talking with my auto mechanic yesterday about the carbs on my kz650. I mentioned that I'm going to rebuild them due to fuel filling the air box. He showed me a little tool he made up years back with black pipe, an air regulator, and a pressure gauge.

He states that he bench tests his snowmobile carbs with the tool, by placing the carbs in an upside down position, so the floats are pressing the needles into the seats. He then attaches the tool to the carbs with a piece of hose running from the end of the tool to the fuel inlet of the carbs. He then applies 5 to 7 lbs. of air pressure to the carbs, then cuts off the air supply, and lets them set for x amount of time. If the air doesn't bleed off, then the needle and seats are sealing as they should.

Has anyone tried this method before, and was it an acceptable way of checking the needle and seats ??

skooterbum4real wrote: I was talking with my auto mechanic yesterday about the carbs on my kz650. I mentioned that I'm going to rebuild them due to fuel filling the air box. He showed me a little tool he made up years back with black pipe, an air regulator, and a pressure gauge.

He states that he bench tests his snowmobile carbs with the tool, by placing the carbs in an upside down position, so the floats are pressing the needles into the seats. He then attaches the tool to the carbs with a piece of hose running from the end of the tool to the fuel inlet of the carbs. He then applies 5 to 7 lbs. of air pressure to the carbs, then cuts off the air supply, and lets them set for x amount of time. If the air doesn't bleed off, then the needle and seats are sealing as they should.

Has anyone tried this method before, and was it an acceptable way of checking the needle and seats ??

I did the same thing minus the fancy test tools: take the brass seat and needle out (very easy) insert the needle in the seat and apply lips to back of the seat and create suction and see if air goes through.

bountyhunter wrote:

skooterbum4real wrote: I was talking with my auto mechanic yesterday about the carbs on my kz650. I mentioned that I'm going to rebuild them due to fuel filling the air box. He showed me a little tool he made up years back with black pipe, an air regulator, and a pressure gauge.

He states that he bench tests his snowmobile carbs with the tool, by placing the carbs in an upside down position, so the floats are pressing the needles into the seats. He then attaches the tool to the carbs with a piece of hose running from the end of the tool to the fuel inlet of the carbs. He then applies 5 to 7 lbs. of air pressure to the carbs, then cuts off the air supply, and lets them set for x amount of time. If the air doesn't bleed off, then the needle and seats are sealing as they should.

Has anyone tried this method before, and was it an acceptable way of checking the needle and seats ??

I did the same thing minus the fancy test tools: take the brass seat and needle out (very easy) insert the needle in the seat and apply lips to back of the seat and create suction and see if air goes through.

:woohoo: I would end up swallowing the needle and seat trying that... :laugh: Not sure how well I would digest the parts !!

Check to make sure the fuel valve or petcock is stopping the flow of fuel when the engine is stopped.

Inspect the brass parts for wear or pitting. The 81 manual has a drawing showing how a wear ring can form. Mine looked good, but I went ahead & polished them with brass wool. Some guys use a q-tip & chrome polish. If they're worn or pitted, get new. Also, the seats should have washers on them.

skooterbum4real wrote: I was talking with my auto mechanic yesterday about the carbs on my kz650. I mentioned that I'm going to rebuild them due to fuel filling the air box. He showed me a little tool he made up years back with black pipe, an air regulator, and a pressure gauge.

He states that he bench tests his snowmobile carbs with the tool, by placing the carbs in an upside down position, so the floats are pressing the needles into the seats. He then attaches the tool to the carbs with a piece of hose running from the end of the tool to the fuel inlet of the carbs. He then applies 5 to 7 lbs. of air pressure to the carbs, then cuts off the air supply, and lets them set for x amount of time. If the air doesn't bleed off, then the needle and seats are sealing as they should.

Has anyone tried this method before, and was it an acceptable way of checking the needle and seats ??

my similar method
carbs off the bike. Bowls off. Carbs upside down. Blow into the fuel line or a clean new piece of fuel line. If the needle are not seating you will know pretty quickly. I don't think i can blow hard enough to left a properly seated float

his method seems more precise but mine doesn't require special tools

Makes my cheeks hurt. :lol:
Steve

If you have new needles and still think you not sealing I learned a trick from an old service department manager. Put a Q-tip in your drill chuck and a drop of Brasso on it. Spin it onto the seat and a lot of time u can smooth out any imperfections. This is really helpful if you have non removable seats.
Ken

I didn't know about the polishing method ?? I may have been able to save the original needle and seats had I known this.....

Good info !! Thanks guys !!

I did the Q-tip and brass polish thing early this spring.
They really looked good so I threw the new replacement ones in a bag and reinstalled the 38 year old ones!!
Even with a high float level, no leaks from those needles and seats... ugh... my old ass bowl gaskets leaked a bit when I'd tip the bike on the center stand.
And the new gaskets did too... they took at least a week to swell up and stop dripping.
Then I reset the float level with the clear tube method and it's all a moot point now.

I always use grease on float bowl gaskets. No leaks.
Steve