Sputtering when legs are on highway pegs and in crosswind

I have an 86 Maxim X 700. It was tuned up by a professional shortly after I bought it two seasons ago just to make sure it was in spec. I noticed sometime after the tune up however that at highway speeds when I put my legs on the highway pegs, the bike would start to hicup and slow down. I have to give it more gas and hold it to get back more speed. If I put either leg down the problem goes away. Just recently I noticed that a STRONG crosswind has the same effect. I believe it did this before the tune-up but just hadn't really confirmed it. The air filter looks good. Otherwise it runs like a top, has great power etc.
I had an 85 Maxim X with the same highway peg settup and never had this problem.
Any ideas?

 

Are the intake boots cracked?

 

When the sputtering occurs, ... set the Pet0ck to PRIME and see if the Sputtering goes-away.

 

Intake boots, throttle shaft seals? is your leg hitting the petcock?

 

Pant legs flapping against the plug wires?

Does the bike have a stock intake, or pod filters? The stock air intake is under the seat, so that would kill that theory. (Aero affecting intake air availability.)

Maybe air blast effect on a loose plug wire or two?

 

Intake boots look good and everything around them. Not hitting the petcock or plug wires with anything. Loose plug wire may be an option... It also killed last year in the rain (but only once) which we thought might be plug wire, but seems like it would be more intermittent. Stock intake. I'm not sure what throttle shaft seals are.
RickCoMatic, what are you thinking that setting it to prime would do?

Thanks everyone!

 

the throttle shaft seals are are the 2 seals on the outside of each end of the throttle shaft (butterfly) on the carb. they are probably old + brittle... notorious for leaks too (either old or not installed correctly)

My thought was that you might be essentially dialed in for air leaking in around the seals (or intake manifold boots). Strech your legs out, changing the airflow dynamics around the seals/boots... and you instantly just got richer... well your mixture anyway

get your bike running on idle and take an UNLIT propane torch around the external throttle shaft seals on the 1+4 carb and see if the revs go up. if so, you got bad seals.

 

Just to clarify a tad; there are (2) throttle shaft seals in EACH carb, the only ones you can get to easily are the outside ones on #1 and #4.

 

I would think that the fuel turns out too lean (not too rich) when he spreads his legs because then there is more air allowed to enter the carbs through the shafts seals, but I could be wrong, it happens all the time.

 

If the air intake is stock, the shift in sitting position with legs stretched could cause the seat to obstruct air intake. Especially if the rubber boots under the seat are cracked/missing.

 

The rubber boot untder the seat was cracked slightly and is brittle. In general it's not a very good fit, so I'm thinking it might be this, though I'm going to check the other seals described as well. I take it there's a non-stock intake that's recommended?

 

Could the added pressure on the seat when putting feet on highway pegs be shorting electrics under seat?

 

Intake boots look good and everything around them. Not hitting the petcock or plug wires with anything. Loose plug wire may be an option... It also killed last year in the rain (but only once) which we thought might be plug wire, but seems like it would be more intermittent. Stock intake. I'm not sure what throttle shaft seals are.
RickCoMatic, what are you thinking that setting it to prime would do?

Thanks everyone!

 

I was typing a message and the web page timed out... not sure why/how it re-posted my old message... anyway...

Myron, we had similar thoughts. I removed the tool box holder thinking the added pressure was just enough to restrict the air flow. That wasn't it.

But I think it was the intake boots after all. I was more concerned about the side attaching to the carbs since they weren't aligned properly on the bottom and the clips weren't tight, but failed to notice that on the side that attaches to the air box two of them seem almost too small. There were gaps on the inside. I cleaned them up with rubbing alcohol and plugged the gaps with rolled up electrical tape, then tape over the top. The test drive seemed to work! It should be warmer tomorrow so I can give it a better test ride. I'll let you know. Thanks again everyone!

 

No, the stock intake is highly recommended; it's just that so many folks tend to modify theirs in one manner or another that we need to ask about it.

The carb-to-airbox boots SHRINK over time; the only true fix is to replace them.

 

So it's definitely the air intake boots. The tape up job solved the problem 90%. Also changed the plugs which were way over gapped, changed the oil and synched the carbs. It's amazing how well it ran with so much out of spec!

Once I get the boots on I'm going to check the rest of the system.

Any suggestions for where to get the boots? A quick internet search didn't turn up much. I'm sure there's new rubber out there that will work, just a matter of finding it.

 

Top right of every page. Oval shaped thing that says "click here for catalog".

 

OK... slightly off topic, but check your coils for cracks... dying in the rain is a classic symptom of cracked + dying coils.... there has been a lot of coil related issues popping up lately.....