B400 - Gearbox sprocket/chain noise

[bdouvill]

Hi,

Two weeks ago, I read the 2nd chapter of B400 Service Manual and noticed that the chain tension must set with 25-35 mm of free movement. I believed that it was rather 35-45 mm so I understood my chain was not tensed enough and decided to increase its tension.

So I did and it started to make an awful noise when riding at very low speed. Then the motor covers this noise, but at idle, it is really noticeable and also annoying. You can even hear it when you push the motorcycle. So the only solution to decrease this noise is to decrease the chain tension which is I believe not a good option either.

I started to think about and as long as I can remember, the bike always made this noise. I got 4 years ago. It had 66000 km on the odometer and now has 80000.

My comprehension is that the bearing of the gearbox output axle might be in a bad shape and it might makes this noise. Increasing the chain tension puts more tension on this axle, so on the bearing.

According to Suzuki exploded views, this bearing is 22x56x16. As usual, Suzuki spare parts price is 70 euros, but I believe I can find the same for 10 to 20 euros on the Net.

My main issues is that removing the gearbox means, according to the service manual, remove everything else in the engine. This is probably super interesting but this is currently my only transportation mean so I can not stay for too long without it running. Plus unbuilding the whole engine implies rebuilding it with a lot of new stuffs. I plan on doing this when I can afford for another bike, I plan one keeping the Bandit.

So guys, what is your opinion on my issue? Any clue this might be a worn bearing? Anything else?

Many thanks in advance for your inputs.

[greg737]

The way to test and diagnose the bearing on your gearbox's output shaft is to isolate it from everything else so you can hear it rotate.  This means listening to the gearbox output shaft spin without any engine noise or chain noise or road noise, etc.

You'll do this in a quiet place like your driveway or home garage. 

You need to prepare the motorcycle: remove the counter-sprocket cover, then remove the counter sprocket itself, then get the chain out of the way and make sure the gearbox is in neutral.  Now you have everything disconnected from the gearbox's output shaft. 

(Because the motorcycle gearbox is a constant-mesh type all twelve of the gearbox ratio cogs will still be meshing and spinning when you rotate the output shaft, so don't mistake their sound for a problem.  The sound you're listening for is the irregular "grumbling" "grinding" of a bad bearing.)

Now you need to set up something to spin the output shaft at a good speed while you listen to the bearing.  Maybe use a hand drill or something similar.  Best to have somebody assist you with this part of the test so you can concentrate on listening to the bearing. 

(I would do this by jamming a short piece of appropriately sized radiator hose onto the counter-sprocket splines and then have your assistant hold the nose of the hand drill against it to spin the output shaft.)

While your helper spins the output shaft you can listen to the area around the bearing with an "automotive stethoscope" or "mechanic's stethoscope".  Most people haven't even heard of this tool, but it exists and it is a wonderful diagnostic tool for things like your bearing.

A good "do-it-yourself" version of a mechanic's stethoscope is to simply use any long, solid piece of metal.  My father used to use a really long socket wrench extension as his mechanic's stethoscope.  He would touch one end of it to the metal near the suspected bad bearing and cup the other end to his ear with his hand.  I know this sounds funny but works, you can really isolate what you hear and as a result you can hear if the bearing is bad.

 
 

[ventYl]

before you start this process. with 66km on tacho bike should have two or three replacements of chain kit. you did 14000 km on current kit. if it was not new it is possible that source of noise is old chain. in service manual, there's specification for chain prolongation limit. check it if the is not just too old which could make such noises.

[bdouvill]

before you start this process. with 66km on tacho bike should have two or three replacements of chain kit. you did 14000 km on current kit. if it was not new it is possible that source of noise is old chain. in service manual, there's specification for chain prolongation limit. check it if the is not just too old which could make such noises.

Thanks for the input. I replaced the chain already with a brand new re-inforced AFAM kit one that I got with the bike. The one on the bike was completely dead, the length between rings was quite different depending on where you looked at it. So tension was impossible to set, I replaced it with the new one which was closed by the way so I had to remove the rear swingarm. I  made that change one year ago, I put sth like 4500-5000 km on it since that.

@Greg737: Thanks for the tip too, this seems a really useful one. Anyway, I wondered if I can use the sprocket to help me turn the gearbox's output shaft? I believe that if it still fits well (no free movement between those 2 parts), that should not interfer within the examination but I can be wrong.

I try to have a deeper look at it when I have some free time next week. Thank you very much again.

[bdouvill]

Some news about my problem.

As I like to understand how my motorbike works, I decided to look into it and see what this gearbox output ball bearing has to say. I removed the engine from the frame, disassemble anything I could, killed the generator in the process (I cut one of the 3 copper circuit; have to make it rebuilt),... Anyway, I learned a lot which makes me happy.

Now, I made some research and tried to be smart. With the bearing dimension indicated on Suzuki diagrams, I tried to find the good reference in advance and found that Koyo ref 6322 NR C3 seemed to be the one (22 euros from a specialist versus 70 euros in Suzuki's catalogue).

Now that I opened the engine, I found that I got wrong... The original bearing and a snap ring like the one that I found, but it also has a pin that I guess refrains it from rotating on itself. I went through the whole Koyo and SKF catalogue. Apparently, they do not make such bearings with a pin... The reference from the original one (HIC 83943 C) seems like a dead end in Google. AllI can find is DR650 users wondering which replacement reference they should use. It seems like no one found out... Anyway, I will have to buy it from Suzuki. 

I also have to find a method to remove the old one from the shaft. I disassembled all gears from the shaft and all I got is the shaft itself, the bearing and the spacer, noted respectively #17, #29 and #35 on this diagram:
http://www.pieces-suz.com/thumbs/s/moto_img/suz_img_15/660_500/DP016053.png

I wonder what would help the most: putting that altogether in the freezer or in my oven? Does anyone have experience about that?

My other question is related the the oil seal of the countershaft. There is one for sure and I have to replace it but I can not find its reference on the previous diagram or on any other Suzuki GSF 400 diagrams. Is that normal? Does anyone knows where I could find that?

Many thanks in advance for your answers.

[greg737]

I also have to find a method to remove the old one from the shaft. I disassembled all gears from the shaft and all I got is the shaft itself, the bearing and the spacer, noted respectively #17, #29 and #35 on this diagram:

Here is a demonstration video (from youtube.com) that shows the type of tool necessary to remove a bearing from a shaft (a puller specifically made for this task).

https://www.youtube.com/watch?v=q38HUzr043c

In the video he is demonstrating the removal of a bearing from a crankshaft, but at the end of the video he confirms that this same type of tool can also be used to remove bearings from transmission shafts.

A good machine shop should have something similar to this tool.

After watching this video you could probably create your own version of this bearing puller from readily available parts.  Maybe even a standard three jaw puller could be used, just hook the teeth under the bearing's outer rim.

[greg737]

Here's another youtube.com video of a guy using the same type of puller.  This puller was purchased from Harbor Freight for $40 U.S.

https://www.youtube.com/watch?v=1yIXnKXQok8

[bdouvill]

Thanks Greg for the tips, I can find the same kind of extractor here in France for approximately 40 euros. The 1st videos only uses the tool and no press.  Here is the shaft with the bearing and the spacer that comes between the bearing and the sprocket:

I should be able to handle it myself.

But I wonder how I will be able to insert the new bearing. I thought about that video: http://www.motorcyclistonline.com/how-to/mc-garage-video-how-to-toolless-bearing-installation
and I thought that putting the shaft to the freezer and eventually heating the new bearing would ease putting it in place. Any clue?

[greg737]

Yes, the heating and freezing method is a very good way to do it.  I put the part that will receive the bearing (this would be the transmission shaft in your situation) into a picnic cooler with dry ice (frozen carbon dioxide) for over an hour and the bearing goes into an oven at 250 degrees F (hot enough to make water vaporize off the part)

[bdouvill]

Yes, the heating and freezing method is a very good way to do it.  I put the part that will receive the bearing (this would be the transmission shaft in your situation) into a picnic cooler with dry ice (frozen carbon dioxide) for over an hour and the bearing goes into an oven at 250 degrees F (hot enough to make water vaporize off the part)

I already read some Ducati owners put their crankcase at 120°C in their oven for something like 1h to be able to extract their crankshaft bearing (they are inserted in the crankcase like in the video), 100°C is the temperature where water turns from liquid to vapor so I believe 120°C/250°F is the adequate temperature for the bearing. For the shaft, I believe my freezer is around -4°C to -6°C (20-25°F) so it should be fine too.

I let you know when I can arrange to extract the old bearing first.

[bdouvill]

Some news about my engine ;-)

First about this ball bearing. After opening the engine and removing the shaft from the gearbox, it was clear that the bearing was not fresh. When I rotate it, it is not noisy because there is no tension on it and I spin it rather slowly but the rotation is not 100% smooth. Probably one or many damaged balls inside the casing (the balls are protected). So I was not wrong about the root cause of the engine noise ;-)

Now to remove it from the shaft, I followed Greg's advice and bought a 40 euros tool. See the result here:



It broke like one second after I started screwing the main screw. I know it was rubbish but I did not imagine that much... Finally, I gave it to a mechanic near my place. He owns a 30T press and told me he fought really hard to remove the old bearing (...), had to add heat to the equation to remove it. To put in place the new one, he stored the shaft in the freezer and heated the new bearing and it was straightforward. Cost me 41 euros.

So I mounted all gears back with new circlips as mentioned in the manual:



and put it back in the engine:



and the other half:



When I tried to put the two casing together, it was ok but I had like 1mm of space between the two especially, right between the two shafts, on the sprocket side :-( Had to remove and clean everything (especially all the casing paste I just put), removed the 2 shafts, put them back again and noticed that using a soft hammer managed to put them both perfectly in place this time. Put again together the 2 casing with fresh casing paste and they fit perfectly this time.

Engine is now back into the motorcycle frame. Still have to mount the clutch, the signal generator and the stator/rotor of the power generator. But I put the drive chain back in place with proper tension and it turns well without noise on the engine side (even with no oil inside for the moment) 

[bdouvill]

Some info and pictures about the disassembly process.

Removing the signal generator requires a special extractor that none of the 2 Suzuki dealers near my place have... Had to buy it online, for 54 euros. It is a Motion Pro one:



Removing it requires also the same kind of tools used to mount/remove screws from your car wheels (no idea of the english name, we call that a pistol in french), can be either pneumatic or electrical:



Also removing the rotor from the electrical generator made me damage the stator (I screwed too far inside the rotor, rookie mistake):



Had it repaired by a professional, took me 71 euros to repair all damaged copper wires (hopefully or not, it was only one of the 3 wires damaged in several places). What a shame, I tested it in November last year and it worked really well, I hope it will keep working.

For info, removing the rotor requires a 68mm diameter extractor, together with a pneumatic pistol.

[Chris H]

Good to hear you nearly finished the repairs.

Its to late now but can I just say for anyone rebuilding that you can split the engine without removing the starter clutch, so saving money by not buying the puller.
You only need the puller if you have to remove the starter clutch to replace a crank shaft.
You must have a tool to remove the flywheel as it has a three pin plate behind it that holds the casings together and as you found out its very easy to damage the coil below if you screw through the flywheel too far.

The gear shaft bearing is a weak point on higher mileage bikes.

I usually grind the old bearing off and then press fit the new one.

Will be a good feeling when it kicks back to life.

[bdouvill]

Here are some news.

The bike has been back to life for more than a month now. Engine started at first try, carb sync does not seem to be needed, works like a charm. 

Bearing whistling is gone. Now I can notice other noises, probably front wheel bearings ;-)
Charging system works fine too as long as I ride more than just to go to work, the alternator has been well repaired.

I changed the front tyre that needed replacement before I went for the bearing replacement. I already put 700 km on the odometer since end of March: used it to go to work again, put some miles of highway around Nice in traffic and this week, I got a 130 km trip in the mountain including the very end of the Napoleon road and a 110 km round trip from Antibes to Frejus following the Mediterranean sea.

Some pictures:



And for the first time in 5 years, I went to the car wash:


Finished on 3 cylinders but now it's ok.

Thanks again to everyone for all the advices and the support 

[Gouraami]

Nice work!

Glad she is back on the road again, she/he looks good

I like the tank protector