Author Topic: 92' B400 just purchased, problems however (Read 4345 times)

ktmiswfo · « **on:** March 16, 2006, 12:56:29 PM »

Hey guys, I'm a newbie here since I just picked up this bike. To give you a brief history I went to my local cycle shop and asked them if they had any bikes laying around or something that was abandonded that I could pick up cheap, they said yeah, a 92' bandit. This bike only had 2000 miles on it. I told them I would give them 1000 dollars for it, they took it, and I have a bike. The reason the guy took the bike in there was because the #2 and #4 cylinders don't have good compression, something is wrong there. 1 and 3 work great. The bike starts and runs, but runs bad because of the lack of compression. Like I said, it only has 2000 miles on it and has barely been ridden. I heard that these are notorious for having black box problems, is this true. What would you do if you were me? Is the black box the same as the igniter box? I know you guys can probably help me out. Thanks.

Red01 · « **Reply #1 on:** March 16, 2006, 01:27:09 PM »

You'll see it referred to as black box, ignition box, ignitor box and even CDI box (though it is NOT a CDI). Ignition problems with this part are not uncommon, but we have the resources here to deal with it if they become a problem for you.

There's a thread on a big bore kit that you might be interested in since you have low compression in two holes already...

ktmiswfo · « **Reply #2 on:** March 16, 2006, 01:39:58 PM »

so do you think this is my problem, I don't want to mess around too much with the motor, I'm a stock kinda guy. I just want it to run correctly first. What would anyone here check first?

PitterB4 · « **Reply #3 on:** March 16, 2006, 01:45:07 PM »

and

Since you're new here, I'll warn you - I'm not the technical expert of the board by a LONG shot!

Having said that... the CDI/ECU/Black Box thing would not have any impact on "compression". It simply controls the spark. It can cause you to loose two cylinders (typically 1/4 or 2/3, not 2/4) if it stops sending the proper signal to one coil or the other. Those cylinders are still going to have compression unless there are other problems.

Red01 · « **Reply #4 on:** March 16, 2006, 02:00:50 PM »

Quote from: "PitterB4"

Since you're new here, I'll warn you - I'm not the technical expert of the board by a LONG shot!

But he is learning fast! And what he said is true. A 2/4 problem is unlikely to be caused by the black box and certainly not be the cause of a compression problem.

A compression leakdown test would be helpful in determining what's causing the compression drop.

ktmiswfo · « **Reply #5 on:** March 16, 2006, 02:07:22 PM »

Actually, I'm unsure if it's 2/4, I just know that it's two cylinders out of the four. Compression leakdown test? I'm new to street bikes. I've been racing MX for 11 years, so maintenance is not a problem. But this is a different side of things. Thanks.

BrianM · « **Reply #6 on:** March 16, 2006, 02:26:36 PM »

There is no "Compressoin leakdown" test, they're 2 different things. A Compression test is quick and easy, hook a guage up to the sprak plug hole, open the throttle and thumb the starter button. You'll get a PSI reading.... kinda like this:

A Leakdown test requires a source of compressed air, a regulator and a set of guages. You hold the cylinder you're testing at TDCC (Top Dead Center Compression) and lay on the pressure. The guage will tell you what pressure is being fed to the cylinder, and what pressure is Actually in the cylinder. Further, you can listen to the exhaust, intake or oil blow-by passage for air to further diagnose where the issue may be.

If I were in your shoes, I'd verify that 2 cylinders have low compression. I'd verify that the plug wires are all on their correct cylinders, and test for spark. If there's no spark, then diagnose that first... if there's low compression, adjust the valves first and then get the bike running and run it fairly hard... it could Very easily be stuck rings (common on bikes that've sat for awhile). If there were still problems from there, I'd look into more expensive options ~ but everything to that point will cost Minimal $$$, mostly just time.

duane · « **Reply #7 on:** March 16, 2006, 02:45:50 PM »

Quote from: "PitterB4"

the CDI/ECU/Black Box thing would have any impact on "compression".

Maybe a typo, but correct me if I'm wrong, maybe Rob meant to say, "Black Box thing would NOT have any impact on compression."

PitterB4 · « **Reply #8 on:** March 16, 2006, 03:02:13 PM »

Quote from: "BrianM"

If I were in your shoes, I'd verify that 2 cylinders have low compression. I'd verify that the plug wires are all on their correct cylinders, and test for spark. If there's no spark, then diagnose that first... .

Good thought! A friend (Cdyer77) bought a non-running B4. It actually had the leads LABLED with pre-printed little stickers, TOTALLY WRONG.

Last summer, I was down two cylinders intermittently. It turned out that the little spade plugs that connect the coils to their supply wires were loose. (Again

) The plug wires are notorious on the little monsters, too.

Hanging out here as much as I do, problems like this turn out to be ignition/spark or fuel/carb far more often than mechanical problems with the motors. Just my $.02.

Red01 · « **Reply #9 on:** March 16, 2006, 04:22:00 PM »

Dirtbikes, streetbikes, cars... doesn't really matter, the mechanical principles are the same.

Kinda pickin the fly shit outta the pepper there Brian on the leakdown test comment.

Here's what a leakdown tester looks like:

While the compression tester Brian shows will tell you if a cylinder is good or not, a leakdown tester does a better job of telling you why a cylinder is low.

If the plug wires weren't on two of the right cylinders, I'd be surprised if it would even run since it would only have two firing at the right time.
If you have low compression on two, they will still fire, they just won't put out as much power as the good ones.

PitterB4 · « **Reply #10 on:** March 16, 2006, 04:58:25 PM »

Quote from: "duane"

Quote from: "PitterB4"
the CDI/ECU/Black Box thing would have any impact on "compression".

Maybe a typo, but correct me if I'm wrong, maybe Rob meant to say, "Black Box thing would NOT have any impact on compression."

Yeah - i saw that too. Musta corrected it just as you were typing. My bad!

Herr Tod · « **Reply #11 on:** March 16, 2006, 05:23:01 PM »

It does run on 2 cylinders. Max speed about 120 km/h

gsxr400 racer · « **Reply #12 on:** March 16, 2006, 11:52:53 PM »

Quote from: "Herr Tod"

It does run on 2 cylinders. Max speed about 120 km/h

Great lmao, keep doing that then see me for a big bore kit!

bonobandit4 · « **Reply #13 on:** March 17, 2006, 12:47:20 PM »

Quote from: "PitterB4"

The plug wires are notorious on the little monsters, too.

I just had a brittle plug wire break off completely this weekend! I was just checking to be sure it was fully seated.

PitterB4 · « **Reply #14 on:** March 17, 2006, 12:50:26 PM »

Quote from: "bonobandit4"

[quote="PitterB4
The plug wires are notorious on the little monsters, too.
quote]

I just had a brittle plug wire break off completely this weekend! I was just checking to be sure it was fully seated.

Yup, that's the way it goes! Luckily, you can replace them all for <$10.