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Bike Runs Great Without Airbox Cover and Filter...

  • Thread starter Thread starter Westy62
  • Start date Start date
W

Westy62

Guest
Continued fron CV Carb Issues.....

Yeah, about the 1/4 throttle. blues....I now found out if I take the airbox cover and filter off the bike will fly! Put the airbox top on without the filter, and it gets a little better, add the filter, and it's worse.....It's very sensitive to how much air is blocked.

I will look everything over again.....New intake boots, o-rings, filter, carbs cleaned and set way too many times now....Still WOT (or what seems to be needle

P.S. If I rev up the bike to about 5-6k without giving it much throttle (e.g. 30 mph in second) and then give it the WOT, it will catch and go for a second or two before losing it's umph. Lower rpm blasts usually don't get to the "go" part....so it's really a velocity issue.

I was thinking about moving the needle up to see if any extra fuel could jump start the flow better, I was even told to drill out the hole bigger in the slider (like a jet kit), so it would slide up easier, but I would prefer not to do that yet!!

TY
 
If the bike runs better without air filter then you are getting too much gas, I think.

What type of bike is it?

I would check the position on the needles and verify they are correct.

Also I would check the jet numbers to make sure they are stock.

Maybe you can just switch to intake pods. Alot of folks like that look. But your mpg will suffer.
 
DimitriT said:
If the bike runs better without air filter then you are getting too much gas, I think.

What type of bike is it?

I would check the position on the needles and verify they are correct.

Also I would check the jet numbers to make sure they are stock.

Maybe you can just switch to intake pods. Alot of folks like that look. But your mpg will suffer.
Click to expand...
Your right.It's getting too much gas.check you plugs and see what they tell you.you might need to rejet if you want the airbox and filter in.I personally dont like pods.If it rains your kinda screwed.I only have a 650 so it's just a waste of money to try to beef it up.I get good gas mileage with just the stock stuff on.Plus Im an old fart anyway.
 
Sorry about not mentioning the bike! It's a 1980 GS450E with 9k.....WOW, too much gas makes sense, but the plugs look lean (almost had a whitish look to the edges of the electrode), and I've NEVER smelled gas so I assumed it was lean. I'll get the carbs off again tomorrow after I do a WOT plug chop....this has been a month long headache, at least the bike runs OK running around town. TY:-s
 
Also keep in mind that even stock jets can be drilled out.

That's how I found my carbs which were running rich.. the PO had the idle jets drilled out.

If your plugs are white when you're idling then that just shows you are len on idle. It doesn't tell you much about other throttle positions. You need to do plug chops.

At least you only have 2 carbs to deal with.. :)
 
I was trying to get my 82 GS300L on the road again after 10 years and had cleaned the petcock. While reassembling it, I bent the spring in it and the bike would barely run with "carb problems" until I got a new one and replaced it. I really did not think it would have anything to do with the way it was running, but it ran like new. This may or may not be a part of the problem, just a FYI.

David
 
Sorry, :oops: I just read the CV carbs you posted and noticed you have a new petcock.....
 
NP.....I'm not sure how to tell the jet size, I'll have to maybe take them in (the jets) to a shop who knows more. The bike is very stock and original all around, so I assumed it wasn't messed with. I'm going to do a WOT plug chop now and post some pics. TY!
 
Carbs check out good again!

Carbs check out good again!

Well, the carbs check out good again, along with all the other intake components.....Could this silly problem be ignition? I have a spark on each cylinder when I pull the plugs out, and the bike runs out well at WOT with the airbox cover and filter off, so I haven't concentrated on ignition for this problem, but nothing is helping in the fuel/carb area.

Any ideas before I dig into the ignition? My Clymer manual has quite a few test procedures, but I need a new ohm meter first!

Thanks!
 
I may be jumping in late here, but have you vacuume synched the carbs and set the valves yet?
 
They've been bench synched and the valves were adjusted this spring. It idles and runs under 1/4 throttle great, but as soon as I crack the throttle past 1/4 it starts to garble, and if I open it up WOT, it will just fall and would almost eventually die (with the airbox cover and filter in). It seems to fire enough to keep it going about 5-10 mph at WOT, and if I let up on it, it will go back to idle. With the airbox cover off and the filter out it flies! The bike will rev in neutral fine also. This is really getting old!

I'm going to wear out my welcome here trying to fix it!

TY
 
If you are certain the carbs are clean you might want to recheck float heights. That has alot to do with how a bike runs in the range you are experiencing trouble with.
 
Plug chops explained

Plug chops explained

I don't really have anything to add here. I just wanted to find out what "plug chops" were. At http://faq.f650.com/FAQs/SparkPlugFAQ.htm I found this:

Plug Chop and How do I do it?

Plug Chops are what you do to tell which rpm range is rich or lean if you don't have an Oxygen or Gas sensor.
  • Basically you run the bike under load, (some do it at a certain rev range e.g. idle, 2000-3500, 3500-4500 etc) however...
  • It is MUCH BETTER to make marks on your Kill Switch casing at 1/4, 1/2, 3/4, Full (WFO) and put a pin in your throttle rubber so you can calibrate the throttle position, NOT the rev range)
  • Then hit the kill switch, wait for the bike to cool, take out your plugs and "read" them for soot (Rich), Colour, Aluminium Bits (bad).
  • Waiting for them to cool is recommended by most people due to Thermal Temp Diff. around plug threads. So it can be a Long term thing and a Royal PITA. An Idle Plug Chop is easy, because you do it every day, when you turn off your engine.
  • START with NEW Plugs or you'll fool yourself.
  • Hitting the "Kill Switch" is called "chopping" the plugs as you get the colour they are at that range, rather than at idle, which is where you normally turn off your engine (right?).
  • Take out your plugs and check the Colour. Generally a nice "Tan" colour in the rpm range you are testing, is what you are looking for. Lamb Chops are tastier though.
  • See this very good site http://www.nightrider.com/biketech/spkplghnbook.htm for a guide to Reading Plugs and Plugs in general.
  • See the Exhaust Rejetting Spreadsheet for additional performance-related Spark Plug Issues.
That's it, just something for the noobs, like me, in case you were wondering.

Thank you for your indulgence,

BassCliff
 
Last edited:
Westy62 said:
They've been bench synched and the valves were adjusted this spring. It idles and runs under 1/4 throttle great, but as soon as I crack the throttle past 1/4 it starts to garble, and if I open it up WOT, it will just fall and would almost eventually die (with the airbox cover and filter in). It seems to fire enough to keep it going about 5-10 mph at WOT, and if I let up on it, it will go back to idle. With the airbox cover off and the filter out it flies! The bike will rev in neutral fine also. This is really getting old!

I'm going to wear out my welcome here trying to fix it!

TY
Click to expand...

Sounds like a LEAN condition as most everything else has been ruled out. Are your bowl vents open? What confuses me is that you say it runs better without the filter and lid...certainly not the norm. :? Is there a chance that your filter is over oiled? If not, and it were me, I'd have to pull the bowls and take another look at the jets and the float settings, though if it runs hard through all ranges without the filter, it would seem to be getting enough fuel... :confused:
 
Here's my WOT plug chop from yesterday, I'm going to get new plugs right now to check them again.....Any clue how much vacuum a little 450 twin should pull? I hooked up a vacuum guage (my car one, but should work?) to the vacuum petcock on the left carb, and there was NO reading, but there's suction there!

WOT chop Yesterday

Plugs012.jpg


Plugs011.jpg


Idle and light throttle chop from 2 weeks ago

Plugs002.jpg


Plugs001.jpg
 
Main jets are too large or needle position is way too high or floats set too high, or a combo. The first set of photos are classic RICH condition...which would explain why it runs better without the filter / lid. Idle looks a little lean for my taste.
 
Just when you think a bike is bone stock (I have the title from the original owner).....You find something like this after a month of headaches.....On the left is the 115 main I picked up at the salvage yard, and on the right is the one that's in the bike (2 of them).....Someone hogged these things out to about 200!! No wonder my CV carb issue/airbox problem has plagued me!!

Running a bit rich??

I'm going to put the right jets in and be done!!!

For sale also.....(I had a chance to buy my boss's bike).

Thanks everyone for putting up with my problems, I am soooooo relieved to find this!!

Wes

Jets002.jpg
 
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