Running engine with no air filter

M

manas

Been Around the Block
As you've already guessed from the title, yes I'm new to tearing apart motorcycles. So this is a quick question:

I just took apart my XS750s air box to replace with conical air filters. In the meanwhile I've been cleaning the carbs and will be performing other small maintenance. Is it OK to troubleshoot the motorcycle by starting it up with pretty much no air filter and a naked carburettor? Probably a stupid question but I thought its better to ask then do a facepalm later.
 
Yes it is okay, so long as you dont suck anything into the engine.
Also youll be running lean and it wont run well most likely.
For a test to see if it will start and run sure go for it, but riding it no, and tuning it certainly not.
 
It's definitely a risk......any dirt on the frame, a bug, a loose nut, etc, has a chance to get sucked in.

I keep some Shop Vac filter foam in the garage for just this reason. Lay it over the intake, get some zip ties around there, and you're good.
 
Re: Re: Running engine with no air filter

Big Rich said:
It's definitely a risk......any dirt on the frame, a bug, a loose nut, etc, has a chance to get sucked in.

I keep some Shop Vac filter foam in the garage for just this reason. Lay it over the intake, get some zip ties around there, and you're good.
Click to expand...

Shop Vac filter foam it is then! Thanks for the input guys.
 
As long as you can put up with it not running very well. For example, no point in trying to get jetting right without filters. But for checking ignition or charging circuits, not a problem. In fact I did that two hours ago. No filter just kicked it into life to check charge rates and TPS settings.
 
i understand the damage caused by hard objects, sand, gravel, metal shavings but what does
something as small on fine as dirt do once its thrashing around in the engine do it just speed up wear n tear?
 
Re: Re: Running engine with no air filter

teazer said:
As long as you can put up with it not running very well. For example, no point in trying to get jetting right without filters. But for checking ignition or charging circuits, not a problem. In fact I did that two hours ago. No filter just kicked it into life to check charge rates and TPS settings.
Click to expand...

That's pretty much what I want to do. I haven't got it to start since I bought it (although its also true that I just barely started working on it). I'd like to just see if I can. If I cab check the regulator/rectifier too, that'll be an added bonus.
 
catsy said:
i understand the damage caused by hard objects, sand, gravel, metal shavings but what does
something as small on fine as dirt do once its thrashing around in the engine do it just speed up wear n tear?
Click to expand...

Even the crap floating around in the air will cause wear if it's not filtered out. Ever notice all the gritty stuff that settles on car paint after it's been sitting outside for a while? Depending on where you are a lot of it is metal particles, and your engine is sucking in large amounts of air as it runs...
 
british and italian bikes were delivered with open velocity stacks and ran for decades with no air filters, i run several bikes with no air filters on the street with no problems...it is not the absolute best scenario but to just test run you will be fine unless it is in a dirty environment or engine ingests something ...
 
joea said:
british and italian bikes were delivered with open velocity stacks and ran for decades with no air filters, i run several bikes with no air filters on the street with no problems...it is not the absolute best scenario but to just test run you will be fine unless it is in a dirty environment or engine ingests something ...
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That's why they last so long without air filters. The lower compression from ingesting silica and the like keeps the motor from over revving and the rider from going too fast.... :eek:

Racing Bikes, with frequent rebuilds, don't use filters. Not too many non-racers rebuild their engines after a good ride.

If you want an engine to last a long time, an air filter is a lot better choice then no air filter.

Heck, an air filter with a small leak will cause engine wear. Show's up in the oil analysis. There is no way an engine, driven on the road, is not ingesting bugs,, and sand, and dirt. Ball and roller bearing are more susceptible to silica in the oil then plain bearing. At least plain bearings can allow the silica to imbed in the Babbitt. Silica just destroys the races and rollers on roller bearings.

I would never run an engine without an air filter. It is just a disaster waiting to happen, and a sure way to shorten the life on an engine.
 
Re: Re: Running engine with no air filter

mydlyfkryzis said:
That's why they last so long without air filters. The lower compression from ingesting silica and the like keeps the motor from over revving and the rider from going too fast.... :eek:

Racing Bikes, with frequent rebuilds, don't use filters. Not too many non-racers rebuild their engines after a good ride.

If you want an engine to last a long time, an air filter is a lot better choice then no air filter.

Heck, an air filter with a small leak will cause engine wear. Show's up in the oil analysis. There is no way an engine, driven on the road, is not ingesting bugs,, and sand, and dirt. Ball and roller bearing are more susceptible to silica in the oil then plain bearing. At least plain bearings can allow the silica to imbed in the Babbitt. Silica just destroys the races and rollers on roller bearings.

I would never run an engine without an air filter. It is just a disaster waiting to happen, and a sure way to shorten the life on an engine.
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Not even to troubleshoot?

Sent from my Galaxy Nexus using Tapatalk 2
 
Put something over the inlet. Don't want anything ingested.

At least a screen

There are a lot of "depends" on the issue. Dry dusty windy day. ?? Your getting sand in the intake.
Wet, calm day, no sand, etc.

Boats don't use air filters because it isn't usually dusty on the water, but the big motors always do.




Sent from planet Earth using mysterious electronic devices and Tapatalk
 
I would be worried about the counter balancer chain stretching and the balance shaft smashing into the crank,XS 750's were notorious for this,,,,,good luck on your build
 
Re: Re: Running engine with no air filter

Wee Todd said:
I would be worried about the counter balancer chain stretching and the balance shaft smashing into the crank,XS 750's were notorious for this,,,,,good luck on your build
Click to expand...

Sorry to bother you again, but could you elaborate on that? The manual doesn't seem to have much information about it and a Google search didn't reveal much information on either counter balance chain/balance shaft. Could you give me a 101 on it? Much appreciated...

Sent from my Galaxy Nexus using Tapatalk 2
 
i once ran a thumper with a sock tiewrapped over the carb. sock got sucked in, jammed between inlet valve and piston smashed the whole engine to pieces. Attach the filter properly is my advice ;)
 
Bert Jan said:
i once ran a thumper with a sock tiewrapped over the carb. sock got sucked in, jammed between inlet valve and piston smashed the whole engine to pieces. Attach the filter properly is my advice ;)
Click to expand...

Maybe it was a dress sock instead of a Sport Sock??? ;D ;D

Nut, ouch..that had to hurt....Don't think a sock could get though a CV carb though, too many things in the way....
 
It was an ye 'olde XL500 with normal carb. did hurt indeed as the rear wheel blocked at 90 km/h...
 
Re: Re: Running engine with no air filter

Bert Jan said:
i once ran a thumper with a sock tiewrapped over the carb. sock got sucked in, jammed between inlet valve and piston smashed the whole engine to pieces. Attach the filter properly is my advice ;)
Click to expand...

I'll take that advice. On the other hand, I have to say a sock blowing an engine to pieces is pretty funny...
 
the initial question was could he run the engine without a filter to test it......sure you can as long as there are no loose parts that will end up in the engine or the area is dirty but again there are a lot of people who run bikes without filters on the road with out issues..and again not best but far from disastrous. i have seen 40 to 50 year old bikes that have never had filters on them and still are on stock bores....
 
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