88 Vaccum leak

[chocking]

Picked up a nice 88 with 30,000 miles on it to add to my 84 in the garage...This will be my 4th 1st Gen...just cant get away from the original

 

All good, except that is simply does not want to start or run unless the choke is halfway open or better..Have run a bunch of seafoam through it...Taken all plugs out and they all are the same...a bit wet and dark from too much fuel with the choke open, but otherwise all look exactly the same.

 

The idle when it doe run is up and down.. and at higher speeds do get a bit of light backfire.. which is not unexpected with an overly rich mixture going in...does seem to run pretty decent at higher speeds

 

Thought it might be a pilot jet, and still am not convinced as the PO said he had the carbs cleaned last year...seemed to be accurate on other aspects of the bike...still plan on cleaning those

 

I took a can of carb cleaner and sprayed around the carbs and the rpms rev up quite high..just cant really tell where a leak might be...carb boots, vacuum line or where...

 

Looking for a place and way to better identify possible vacuum leaks..Any ideas...

 

Thanks

 

Clay

[Flyinfool]

There are a lot of places that can leak around there.

 

Start with the air box, is it there?

Is there an air filter in it?

Has the air box been modified in any way?

Is the breather hose connected to the air box and the engine?

 

While the air box is open start the bike and make sure all 4 sliders are doing the same dance.

 

Look at the carb manifolds for any obvious cracking of the rubber. Cracks do not necessarily indicate a leak since there is metal inside of there. But you can then test further to see if the visible cracks are leaks.

 

Check the block offs on the fittings for doing a carb sync, it is common for those to crack with age.

 

Look for missing or disconnected vacuum lines.

 

When using the carb cleaner to track the leak, use the pin point straw and smaller bursts of cleaner to try to localize the leak.

[VerntureVet]

I just went threw this after a carb rebuild. Would Idle high ~1500rpm some times and some times it would calm down. Like @Flyinfool stated you are best off with the pin point straw and hitting areas like the head to carb boot joint. then the boot to carb. and then move onto the airbox boots. Cleaning all that up for me caused more issues than it solved. The stock air cleaner boot clamps stretched I guess over the years and would not tighten hard enough even though they was bottomed out. Had to replace them with hose clams. Also the boots got a little loose where they have the ridge that locks into the air box. I had to put a couple wraps of black electrical tape on them to get them to seal good. On top of that sync screws got out of wack and still would not let the idle come down till proper vacuum and sync was obtained.

 

If the PO said something I would not take it as being done proper most of the time. Even if the carbs were "CLEANED" last year to some that means spraying carb cleaner into the cabs. To others that means taking them apart and doing a soak and spray.

 

Also remember some people are not clean freaks. A lot of times old gunk and crud gets overlooked by a rider and in years that crud is sealing and holding things in place. A proper cleaning can lead you to find sometimes other adjustments got made to adjust for the crud deep in the system. Cleaning said crud can make things work better in one area and those overlooked things now become an issue.

 

With that in mind my cruddy carbs had sync screws opened up to make up for the nasty build up that was obstructing flow. cleaning them threw them out of wack.

[cowpuc]

Start at the bottom and work your up with the spray, that way if its a leak in the lower area it wont be triggered by spray running down - leading you to a false location..

[chocking]

Thanks for the tips and ideas..Really appreciated...I've had a couple folks suggest using a small propane torch....( obviously unlit) to test around areas instead of spray....less mess...but as effective???

[Flyinfool]

Less mess but if the propane builds up, it can get real interesting real fast.

[cowpuc]

Less mess but if the propane builds up, it can get real interesting real fast.

 

Yea Jeff,, but think of all the hot dogs he could roast after the interestingness wore off

[cowpuc]

Thanks for the tips and ideas..Really appreciated...I've had a couple folks suggest using a small propane torch....( obviously unlit) to test around areas instead of spray....less mess...but as effective???

 

I have used both many times.. Usually I save the propane method for checking crank seals on two strokes cause I am looking for at a specific item (one seal). The problem with using when many items could be the issue and they are all located in the same area is that your dealing with a gas and its hard to control to one specific point.. Liquid works better in the application we are talking..

[van avery]

Start at the bottom, Yes.

There are ORINGS under the bottom on the intake boots. Replaced mine and it helped.

Also make sure the carbs are completely seated in the boots.

[capymotiv]

I use a piece of hose attached to the vacuum port of the boot and blow smoke in from a cig or cigar or something. May take a couple puffs but pretty good at finding leaks. Just look for the smoke.