First of all, hello everyone :)
I've been lurking about this site for quite some time and have gleaned a lot of valuable advice - I'm hoping to get some more.
I bought a running but rather dilapidated Bandit 400 a few months ago on impulse (always a fan of the two strokes and 400's). She always had problems starting and would take a good 30 seconds to take life, but broke down completely a little while ago, and the carbs kept flooding (vacuum pipe was connected and the tank was not set to prime).
Here's what I know so far:
1) She was running very rich - fouled a new set of sparkplugs (CR8EK) within a few weeks and I got horrible mileage.
2) The carbs seem to be from a GSXR - the main jets are 97.5, not the 100/110 that are stock on the Bandit. It was possibly due to a jet kit as well though.
3) The jet needle has 6 heights, and the clips were on 3.
3) She has an aftermarket 4 to 1 performance exhaust.
4) The original airbox is in place, but there is no foam inside, just the mesh.
I've ordered an O ring kit from Litetek, kit A (http://litetek.co/Carb_Kit_Suzuki_GSF400.html) and will have the battery back up to charge by tomorrow after standing, and fit the O ring kit. Additionally, I'll strip the petcock down and make sure it's all okay.
Here's where I need help:
1) The battery: I found another thread online which stated that replacing a 120CCA battery with a higher spec solved a lot of starting issues. Should I consider this, or is it likely that my starting problems are carb related?
2) The carbs: the pilot jet (?) on the number 1 carb seems to be fouled slightly - is this still a usable part? See here: https://www.flickr.com/photos/panchiaph ... /lightbox/
3) Jet needle: the needles have sound spring seats, but there are no washers below the clips on two of the carbs - can I replace these washers with a normal washer of comparable size or do I need the OEM? Also, the spring seat, clip and washers seem to have been coated in a sort of liquid gasket which has peeled and I have removed. Does whatever this sealant was need be there?
4) Head exhaust bolts: these do not seem to be as tight as they should be, and I'm worried that I was losing compression, hence the slow starting - but how the hell do I tighten them? They have allen key bolts but are incredibly stiff.
The reason for the urgency is this - I had a car accident last week (we have a lot of bad potholes here), and my car was written off - insurance will take a month or so to pay out and until then I do not have any means of transport, which is posing quite a challenge. I'm a university student, so I don't have a lot of budget, but I absolutely love all things mechanical and would like to see this bike somewhat restored by the end of the year - right now I just need to get her running reliably.
Thanks for the help :)
Y
Bandit 400 Advice (Urgent)
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SevenThreeSeven
- Settled in member
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- Joined: Wed Feb 26, 2014 4:45 am
Re: Bandit 400 Advice (Urgent)
A 20-something year old Bandit presents some challenges: You're up against things like: 20 years of normal wear, 20 years of prior-owners and their maintenance methods, your own mechanical knowledge level, your own ability and/or willingness to invest money in a 20 year old bike, and the list goes on...
It is not uncommon for a combination of factors to result in a Bandit 400 which has carbs that simply cannot be tuned.
During the normal arc of a Bandit 400's lifespan it will almost certainly have fallen into the hands of a prior-owner who had "boy racer" aspirations which means the carbs will have been seriously monkeyed with. The main needles are probably not original, they were probably swapped for much richer-running ones at some point.
One problem that Bandit 400 carbs often develop late in life is worn emulsion tubes. The emulsion tubes are supposed to have nice round holes but quite often the needle will have worn the hole into a larger, oblong shaped opening. This condition allows more fuel pass through into the engine, too much fuel, so the Bandit runs way too rich and there's no way to "tune" this condition.
When you have the carbs taken apart you should look at the constant velocity slide springs, quite often the "boy racers" will have cut the springs shorter to make them weaker which allows the slide to slam full open earlier (at least this is obvious to the eye). However, when the Bandit 400 and the GSX-R400 were new (i.e. still in production) some aftermarket performance parts providers were selling "boy racer" carb modification kits that included weaker springs which looked normal to the eye but were much weaker than the stock springs.
A motorcycle's exhaust headers mate to the engine head by way of relatively soft copper gaskets that are designed to crush/deform slightly when the bolts are torqued to the proper amount of force. This is how they are sealed so as to prevent exhaust gasses from escaping at the head-to-exhaust junction. This creates a situation where the idea that "tighter is always better" does not hold true.
It is not uncommon for a combination of factors to result in a Bandit 400 which has carbs that simply cannot be tuned.
During the normal arc of a Bandit 400's lifespan it will almost certainly have fallen into the hands of a prior-owner who had "boy racer" aspirations which means the carbs will have been seriously monkeyed with. The main needles are probably not original, they were probably swapped for much richer-running ones at some point.
One problem that Bandit 400 carbs often develop late in life is worn emulsion tubes. The emulsion tubes are supposed to have nice round holes but quite often the needle will have worn the hole into a larger, oblong shaped opening. This condition allows more fuel pass through into the engine, too much fuel, so the Bandit runs way too rich and there's no way to "tune" this condition.
One of the things that the "boy-racers" are obsessed with is Throttle Response. Because of this obsession they often monkey with the carb's Constant Velocity slides. The "boy-racers" believe in the myth that faster slide action means better performance and they modify the carbs so that the constant velocity slides slam full-open as soon as the engine vacuum begins to develop (causing it to happen way too early). This is often a major contributor to way "over-rich" running.3) Jet needle: the needles have sound spring seats, but there are no washers below the clips on two of the carbs - can I replace these washers with a normal washer of comparable size or do I need the OEM? Also, the spring seat, clip and washers seem to have been coated in a sort of liquid gasket which has peeled and I have removed. Does whatever this sealant was need be there?
When you have the carbs taken apart you should look at the constant velocity slide springs, quite often the "boy racers" will have cut the springs shorter to make them weaker which allows the slide to slam full open earlier (at least this is obvious to the eye). However, when the Bandit 400 and the GSX-R400 were new (i.e. still in production) some aftermarket performance parts providers were selling "boy racer" carb modification kits that included weaker springs which looked normal to the eye but were much weaker than the stock springs.
You need to be very careful about making assumptions like this. First, the tightness of the bolts that hold the exhaust headers to the head has nothing to do with the cylinder's compression. If you go at them and tighten them up a bunch you're probably going to break at least one of them off. Are you prepared/able to drill out and extract broken exhaust bolts?4) Head exhaust bolts: these do not seem to be as tight as they should be, and I'm worried that I was losing compression, hence the slow starting - but how the hell do I tighten them? They have allen key bolts but are incredibly stiff.
A motorcycle's exhaust headers mate to the engine head by way of relatively soft copper gaskets that are designed to crush/deform slightly when the bolts are torqued to the proper amount of force. This is how they are sealed so as to prevent exhaust gasses from escaping at the head-to-exhaust junction. This creates a situation where the idea that "tighter is always better" does not hold true.