Drilled Airbhox???

[Brad]

Just wondering how and why people drill out their airbox? What are the pro's and con's?

[b.walker5]

It's about increasing airflow through the filter. In stock trim the only intake is through the snorkel under the seat and some people feel that just isnt enough so they drill the underside of the air box to let more through. Personally I dont have problems with the stock setup and think it lets plenty of air in for the engines needs, but those who insist on making things 'better' swear by it.

There are also those who believe that it can let water in to the intake, but this is largely false, as the holes don't go directly into the filter housing, but rather into the plenum box underneath, but a little water misting into the intake isnt a bad thing anyway, as long as its misting and not whole droplets.

[natemoen]

Mine had holes when I got it.

[bikerphil]

I run both my stock 79 air boxes with two 1" holes in the bottom center, cut back snorkel, and a K&N, better breathing totally, works for me.

[Brad]

Thanks for the info, I have a K & N and even with my fuel idle mixture screws all the way in, it runs rich. Maybe the extra hole might help.

[bikerphil]

Thanks for the info, I have a K & N and even with my fuel idle mixture screws all the way in, it runs rich. Maybe the extra hole might help.

Could be a lot of things causing a rich condition including a weak spark. You could try running it temporarily with the bottom of the air box off, see if that helps, JAT.

[Brad]

Could be a lot of things causing a rich condition including a weak spark. You could try running it temporarily with the bottom of the air box off, see if that helps, JAT.

I will give it a shot for a bit tomorrow, roads still havent been swept yet though, the city covers them with sand in the winter, thanks.

[petejw]

Thanks for the info, I have a K & N and even with my fuel idle mixture screws all the way in, it runs rich. Maybe the extra hole might help.

hi brad,

if u can screw the mixture screws all the way in (gently seated) without the
bike stalling at idle, sounds like ur pilot jets could be to big,
have u changed them out from stock, some after market kits
that have 42.5 stamped on the pilots are the wrong ones and
run much richer than the stock pilots. jat.

[3Phase]

It could be the carbs are out of synch or the idle circuit is plugged up and the throttle plates have to be opened so far that the transition ports are beginning to be uncovered.

The mixture screws can't adjust the transition ports, only the idle ports and it'll be too rich; three holes extra feeding fuel instead of just the one.

[petejw]

It could be the carbs are out of synch or the idle circuit is plugged up and the throttle plates have to be opened so far that the transition ports are beginning to be uncovered.

The mixture screws can't adjust the transition ports, only the idle ports and it'll be too rich; three holes extra feeding fuel instead of just the one.

i agree if it was 1 or 2 carbs that were doing it,
but if the bike was at idle (1100rpm or lower) and all 4 mixture screws were screwed in at the same time
and that made no difference to the idle or it increased it, then
it would be more likely that the pilot jets are to big,
but for sure u would still want the carbs synced to be certain.

[James England]

Mine aren't drilled and it runs fine. There are definitely aspects of the bike which benefit from being made 'better' than the OEM spec eg rectifier/regulator, coils, fusebox etc but I'm not sure that drilling holes in the airbox is one of them. I don't like the idea drilling great big holes in an airbox that's surviuved 30 years unscathed. I've not fitted a front mudflap for the same reason. They all seem to need drilling of the fender!

[motoman]

There are definitely aspects of the bike which benefit from being made 'better' than the OEM spec eg rectifier/regulator, coils, fusebox etc but I'm not sure that drilling holes in the airbox is one of them. +1 England,and not just for proper look either. There's more to the innards by design for efficient air flow and correct velocity matching with the sidedraft carbs than meets the eye. Same goes for the stock exhaust where each 2 into one meets. In stock form, most power through ALL rpm ranges IS achieved in stock original configuration. Although some don't have alot of choice when putting them back on the road.

[ManagerMike]

Although some don't have alot of choice when putting them back on the road.

Got that in one! My barn dweller was not merely drilled, swilled, and killed, but dented, scratched, and dropped
Some sort of afterthought mufflers had been (ahem) "welded" on, and that was before it had been laid down!
The airbox was an abortion, the tank caved in on the side, engine side covers gouged , RTV IN THE CARBS!!! fer cryin' out loud!! What some people will do to a bike.......

I accuired this bike free of charge, but have no realistic tally of how much money I've put into it, and have not kept track of the hours.

If for no other reason, if and when I do find myself with a different bike, this one will never leave my stable for all of the blood sweat and tears I've put into it making it right and making it mine. I've had many bikes, but never more than one at a time (the wife and kid's notwithstanding). Part of what may be considered my soul went into this machine, and still does.

[3Phase]

i agree if it was 1 or 2 carbs that were doing it ....

Yebbut if it's jetted too rich you have to open the throttle plates farther to get enough air to run at the correct idle speed. That starts to uncover the transition ports and then your mixture screws don't work any more on any of the carburetors.

I guess I'm agreeing with the jets being to rich but didn't write it clearly.

[petejw]

Yebbut if it's jetted too rich you have to open the throttle plates farther to get enough air to run at the correct idle speed. That starts to uncover the transition ports and then your mixture screws don't work any more on any of the carburetors.

I guess I'm agreeing with the jets being to rich but didn't write it clearly.

lol, thats ok scott,
i dont write clearly at the best of times. :-)