Connecting vacuum gauge to engine
 

Hi guys,

I'm wanting to run some diagnosics on my engine - carby version of the KLX250S.

I've got a vacuum gauge which will help me troubleshoot. It says the following in the manual:

Now, where would this port be? I'm thinking I'm going to have to use a T connector to do this anyway, but where would you 'tap in' to measure.

If you intend to take vacuum readings at or near idle, you're out of luck. The intake manifold vacuum pulses drastically.
To answer your question:
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Brewster

The OE carb on my '12 had a port on the top of the spigot where the carb fit into the head. I think that it had some emissions garbage originally plumbed into it but it should do the job. Like Brewster has said, you will get some pretty erratic readings at idle without some way to damp the pulses. The gauge set I use on my multi-cylinder bikes has the ability to do just that.

Back when I worked a the dealerships, I had vacuum "tubes" which are smoother reading than the guages. But yeah, still going to jump a bit. You get use to reading them, but all I ever used them for, was to synchronize multiple carburetors on a bike, never anything else.

Cool, thanks guys. GBAuto, i've got a '12 so that helped a bunch.

Yeah, all of them that had the pollution valve have the fitting and it's no big deal if the valve is unplugged, nothing can be damaged.

If you have problems with the pulsing, try adding a large container (sealed of course) to the hose system and put your gauge coming off of that. A large volume of air should dampen the pulsing.

Werloc, remember the metal box of 4 mounted dial gauges that had a damper adjustment to "steady" the dials of each gauge when synching a set of bike carbs? When the mercury reservoir Carb Stix came out, it was great to have something so simple but so effective.

Yes I do remember those. My guages where mounted on a red metal piece. I think that was just a bleeder valve with a thumb screw, or something like that. I "think" I got mine at motorcycle mechanics school (AMI) back in 1981 when I went there. They sat in my bottom drawer of my tool box once the new stick tubes came out. Man, your bringing back old memories, very old....LOL