Motorcycle Repair: 97 marauder seems to flood on throttle, suzuki marauder, leak down tester

Question
Thanks for getting back to me Mark.

It's never been in a wreck or laid down. I bought it new in 97. The bike has 35k miles on it. I change the oil and oil filter regularly at 3k miles. When I pulled the plugs the front was blacker then the rear. I've replaced both plugs. Air filters were both clean.

I do have slash cut pipes but those have been on there for 6 years.
Never had to store it for more than a week or two. I'll ride as long as it's not below 32 degrees, snowing, or pounding rain. Other than that I'm on it most of the time.

Last tune up was summer of 2003 when it had 20k on it.

Could it be bad gas? I'm going drain the tank and get new. If that doesn't fix the problem it sounds like I'm going to have to take it in and have internals checked. If you've got any other suggestion short of tearing the engine down plese let me know.

Thanks

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Followup To
Question -
Mark,

I have a 97 suzuki Marauder that has recently develeoped a problem where it seems to flood and die when I roll on the throttle. I can't even make itto the end of the block. I've changed the spark plugs and air filters. But the problem still persists. Any suggestions as to where to look next would be helpful.

Thanks
Answer -
Hi Tim,

I'll need more intel to help you diagnose the problem. Please review my instructions where you typed the question.

What can you tell me about your MC?

Any history of repairs and maintenance? Modifications? Crashes? Periods of storage? How old is the gasoline? When was last tune-up? Describe appearance of spark plugs.

Tell everything you can think of for best results. Do you have a compression or leak-down tester? We'll go from there.

Respectfully,
Mark Shively

Answer
Tim,

Thanks for the additional information. With the information provided I suspect the PAIR valve may be the cause of the problem. I copied the below PAIR valve information for your review.

Visit: "www.migcruisers.com/projects.html" for more resources for your Marauder.


Respectfully,
Mark Shively


The PAIR valve on the Marauder and Intruder LC is used to burn off hydrocarbon emissions from incomplete combustion that occurs during deceleration in gear. It works like this:

When you open the throttle on your bike, manifold vacuum drops off since air is entering through the carbs. This air mixes with fuel that is burned in the combustion chambers, more or less completely. When you let off the throttle, particularly in gear, the throttle plate closes, restricting airflow to the combustion chambers, and the manifold vacuum goes way up. This is particularly the case when coasting in gear since the engine is being pushed by the rear wheel at speeds above idle. Since the throttle plates are closed, a high vacuum is developed. This vacuum pulls fuel from the carbs into the engine, but the mixture is too rich for it to burn. It's dumped unburned into the exhaust system.

This is where the PAIR valve comes in. The valve is controlled by manifold vacuum. When vacuum increases (pressure decreases), the valve is pulled open. On the Marauder, fresh air is drawn in through the PAIR's air filter and fed into the exhaust port of the cylinder heads. On the LC, the source of fresh air is from the rear cylinder airbox. That air provides the right mixture to spontaneously ignite the hot unburned fuel exiting from the exhaust valve.

If you have stock pipes, you won't notice this effect. However, change to less restrictive aftermarket exhaust, and the combustion takes place futher down the pipe, resulting in sounds that people describe as backfiring, burbling, popping, etc., during deceleration. The sound you're hearing is the sound of the exhaust gasses burning off. Some folks kinda like the sound, others can't take it.

What can be done about it? You can disable or remove the PAIR valve from your bike. This will in no way affect performance, even a little. All it will do is remove the backfire, and of course, increase hydrocarbon emissions. The valve can be disabled by disconnecting and PLUGGING the vacuum line that controls it, or by blocking its fresh air intake. The valve can also be completely removed from the engine, revealing those beautiful V-twin jugs hiding underneath.

In order to remove the valve, though, the vacuum lines must be properly plugged to prevent air leakage into the manifold, the fresh air inlets into the cylinder heads must be blocked, and in the case of the LC, the fresh air port on the rear airbox must be plugged. You can probably fabricate everything you need to do this, but there's a better way...

Check out Moccasin Mike's website for information on his PAIR valve removal kit. It's a great deal at only $15 and contains everything you need. Detailed instructions for the Marauder and the LC are also included. Mike's website is:

http://www.moccsplace.com/images/pair/pair.htm