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I've never worked on a GS500, but in general there's no need to attach the air box to test the carbs.
More than anything the air box is there to keep big pieces of debris out of the engine. We've managed to re-purpose the air box for a bunch of other smog related things, so things like vacuum hoses are something else that can complicate issues, but most will run without the air box.
To test for leaks, you won't need the airbox. When you go to sync the carbs after verifying all else is good, you'll want the airbox and filter in place. On this particular bike the airbox is actually critical for decent operation. Without it, or with it cut up the airflow into the carbs is too turbulent and screws with them, thanks to their CV design.
Last edited by Kurlon; 04-09-15 at 12:38 PM.
Thanks guys. For fuel, can I just stick a piece of tubing straight up off the fuel inlet and fill with gas?
Sure, I used to cheat and use an old pitbike tank so I had a petcock. Some people repurpose old gear oil bottles that have the pull out spigots and test fuel cells. Just make sure whatever you setup is safe. A tube flopping in the breeze full of gas over a hot engine, may not get you on the front page of the Darwin Awards website but I bet you make Reddit.![]()
Again, no GS experience, but generally yes. It does need to go up.
You'll need more fuel than you think. I usually find some way of attaching a water bottle filled with fuel to a short section of hose.
That sounds like it might only be firing on one cylinder. Did both exhaust pipes get hot? That's the quickest way to tell...
I'd probably find something with less residue than WD40 - like starter fluid.
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You can get cheap infrared thermometers these days, I got one from Amazon for like $15.
The way I check for a spark plug not firing is to pull one plug wire off. Most twins will run (badly!) on one cylinder. Or get an inline spark plug tester for $10 from your local auto parts store.
WD40 or starting fluid is fine. It won't explode, but it will jump like you just twisted the throttle a bit.
Also check that you're running the right spark plugs and that they're gapped correctly.
I'd be happy to shoot down one day and take a look with you if you'd like.
Last edited by number9; 04-09-15 at 09:30 PM.
For a test tank I usually use a tank from a lawn tractor or snow blower. They are the perfect size (small) and usually have a fuel shutoff already built in or in line.
-Christian LRRS/CCS HasBeen ECK Racing
2011 Pit Bike Race CHAMPION!
Not long ago I invested in a Motionpro fuel jug. Money well spent. Sometimes having nice tools is.. well.. nice.
Like this? Auxiliary Tank | Motion Pro
Seems a good idea.
Is that a thing? I've never had problems with carb bowls filling by gravity.
I'm starting to realize that if motion pro makes it, I probably want it.
Last edited by nhbubba; 04-09-15 at 10:13 PM.
You're right, I should have said this: I spend more time tinkering with carbs on cars. And when you're relying on an old mechanical fuel pump to drag fuel 15 feet, sometimes it takes a while
And yeah, Motion Pro make some lovely stuff. And most of it is pretty inexpensive! Summit Racing carry their stuff too
If you really want to learn a good practice is to take every bolt out of the bike and lay it all out. Then use the book to reassemble it. You'll learn everything about how that bike goes together. Maybe you want to figure out what's wrong with it mechanically first and then do that in case you need to rebuild the engine. It'll take a lot longer to learn if you just tackle one problem at a time, but it works if you keep the bike long enough and if it's sufficiently bad off. Running issues are simple if you just follow fuel, compression, spark. Usually fuel is the first and then look at spark, compression is usually an expensive and complex repair.
That was my original plan when I bought the bike, then I got it home and realized it was actually in decent shape. Now I kind of just want to get it running so I can commute on it. I still may do that next off-season.
The next annoyance I am encountering is snapped bolts. I thought the bike was just missing half the hardware, now I am seeing that it is mostly bolts that have snapped off.
You'll need some of 13 Piece Left-Hand Drill Bit Set and probably some 12 Piece Screw Extractor Set (not necessarily from HF, but a set of LH bits and a set of screw extractors will be your friend).
Wrenching on this crap is basically an over-glorified excuse to buy toys tools. You realize that by now, right?
If you ever get married, expect her to never, ever understand.
Learned a few things today:
1. JIS screwdrivers are amazing
2. The heat gun is awesome for stuck fasteners
3. The little cutoff wheel for the dremel is equally awesome for the same
4. Engineers must be wicked smart to make carbs work with all them little holes and shit
I didn't find anything obviously wrong with the carbs except for two missing o rings between the carb covers and carb bodies where the vacuum ports are (I think these are all the right terms). I will start by grabbing some more of these.
Is my bike going to explode if I don't replace all the other o rings and gaskets I pulled out? Manual says to do it, internet says not to do it.
O-rings and gaskets can probably be reused if they aren't too dry / rigid.
It's reasonably inexpensive to replace them while you are in their vs. having to dig back in a couple months from now.
A 3rd party carb rebuild kit may be worth your while. Check fleabay.
These are CV carbs? The "carb covers", is this the top (usually plastic) over the diaphragm on the top of the slide? Missing seals here could cause very, very poor performance. Vac leaks in general are bad. Vac leaks that prevent the slide from working are way bad.
You invest in the $80 harbor freight ultrasonic cleaner yet? That with a dash of simple green in it => carb cleaning nirvana.
And I've been telling people about that re: JIS drivers forever. I wish people would stop using hardware store philips drivers on those butter soft carb screws.
Last edited by nhbubba; 04-15-15 at 06:05 AM.
+1. If you are opening up the system and they are 5-10yrs old then I would replace them. If the system is left untouched and they are not leaking then no need to replace just for the sake of doing it. I always replace orings and gaskets with oem. Many will say not always true and depending how easy it is to replace makes a difference. Base/head gaskets I go oem. Valve cover gaskets which ever sometimes.
2004 SV650
1979 GS 850GN
2005 Tt-r125
NEMRR #246 - Woodcraft / Armour Bodies / Hindle Exhaust / Central Mass Powersports