4th gen snorkel mod causes mine to bog bad

I did a quick search and didn't see any mention of this. but my 4th gen I recently acquired, had the snorkel removed by the previous owner. It bogs like a bike that has a poorly routed carb vent hose.

I spent the last day or two routing and re-routing the vent hose due to serious bogging when there's a cross wind or if I'm over 55 mph and a large truck passes by. I couldn't get the problem fixed, carbs were just rebuilt and synchronized and has a factory pro stage 1 jet kit. 130 main jets, stock pilots. so on a hunch, I took a snorkel from my old 4th gen parts bike and replaced the snorkel, now runs perfectly.

Since I can't seem to find any others that mention this using the search function, should I be concerned my 97 with 30,000 miles is so sensitive to just a snorkel removal? wondering if there's any subtleties I'm missing on carb tuning that could cause this?

 

Is the bogging at a certain rpm range or at a certain throttle position? Is it running lean when it bogs down?

Try it again without the snorkel and pull the choke lever when it bogs to see if adding extra fuel helps.

 

maybe bogging is the wrong word but I'm not sure how else to describe it. it only happens in strong cross wind or if I'm riding into a relatively strong head wind. kinda like if you route the carb vent tubes into a turbulent postion on your bike. Otherwise, it runs great. No lean or rich issues I can tell - no hanging idle, no black exhaust residue but haven't pulled the plugs to check those.

I did play with the chokes and it didn't improve any throttle response any. But I didn't ride with the choke on since the bike only 'bogs' in windy situations.

In any case, we had another windy day today, so I took the opportunity to ride into some pretty strong head winds with no problems - snorkel is now back in. Maybe I'll never figure it out for sure without a dyno but I think I have the carbs set pretty well - based on my butt dyno and experience.

 

my carbs have 130 mains and they are stock un-molested carbs. Nice thing about Factory Tuning besides their customer service number is the fact that they don't require you to drill your slides. One of my bikes has shimmed needles which I don't think really make a difference. You could always get the stock needles again, at least you don't have to JB Weld the holes from a Dynojet kit. :vtr2:

I have a aquaintance/friend (use that term loosly) and he busts my back-side about drilling slides, I can understand the logic about vaccum and slides rising, but wtf? I have drilled dampening rods in forks, but resist doing it on my slides. Other peoples is a different story :loco: Cheers

 

yep drill out the slide holes and then you have to put a step in the needle to allow fuel thru the main jet because the slides won't rise up to open all the way at WOT anymore--good luck with the venturi making that work. Seems like the Millions of dollars of Keihin and Honda's research and engineering efforts might be the better way to go...

 

I pulled the snorkle off of my 86 700... it sounded like a tornado... I then put it back on.. meh the difference was minimal that I could detect..of course that was two years ago.. neighbors hated that intake when it started guzzling air....

 

I tried running without the snorkel on my 5th gen for 1500 miles, didn't like it as it seemed to make the bottom end and lower mid range feel "fluffy" I ended up putting it back in, admit it sounded good in the higher revs.

 

In the olden days, we used drill everything out, air boxes, CV diaphragms, pilot plugs, fins etc... Mostly to little or no effect other than making the bike run like crap. Most modern, 1985 ish and up bikes come from the factory tuned pretty dang good as is. If you add aftermarket bits to it, like pipes, or air filters, you have to retune the carbs to match. It takes a professional with a O2 sniffer to do this right, other wise weird things happen in the powerband. On a Gen4 I wouldn't touch a thing, run it bone stock. My 86 2nd gen has a Kerker on it now, and has gain a little mid range but thats about it....other than being stupid loud. I experimented with removing the snorkel from the airbox, and it developed a flat spot at around 6500 rpm, and would no longer pull redline in 6th. I believe the snorkel keeps the air velocity up at lower rpm, and reduces intake honk.

 

The idea is that the slides will lift faster, giving better throttle response. However, this has to be balanced against other mods on the bike and or no mods. A slight increase in diameter might help in a stock bike, if this is a real issue. If you want throttle response, get a set of non CV carbs. Also if you do drill out the slides, fast response will mean you will have an instant lean spot right off bottom. You will need to fatten up the pilot somehow. Its called dropping the idle needles. Really its the air bleed screw for the idle jet. I do this with my carb bikes when I first get them, because the factory always sets them really lean to get them to pass emissions.