Suzuki van van (RV125) gearbox?

[trevor saxe-coburg-gotha]

[finchy95]

Oh yeah the bike is bombproof without a doubt. It's just this damn gearbox -_-

[finchy95]

So the chain flew off on the way to work this morning and has jammed up under the cover. Yaaaaaaayyyyy!!

[trevor saxe-coburg-gotha]

What kind of condition were the chain and sprockets in? If rusty, this could well explain not only the reason for it breaking but also issues selecting gears. Got any pictures?
____________________
"Life is a sexually transmitted disease and the mortality rate is one hundred percent."

Mobylette Type 50 ---> Raleigh Grifter ---> Neval Minsk 125

[Iain.]

[chris-red]

[finchy95]

That moment when it's your own bike so you know what's going on...

I haven't got any pictures or owt as it was about 06:45 when this happened and it was pissing down so I was trying to find a place to hide.

The chain and sprockets are fairly old 6-8 months maybe? But they're in fairly good nick (no rust etc.) The chain had just over an inch by 5mm at most with me sat on it.

Seriously the chain was tight. I had one snap just after my CBT due to poor maintenance and it wrecked a brand new pair of kevlar jeans and I shit myself because I had no idea what the fuck had happened, so I always make a point of checking.

[UnknownStuntm...]

[finchy95]

*sigh* as I have explained multiple times now, the chain was tight, but not overly so, nor was it overly slack (contrary to your opinion) and I had a work mate of mine check the chain last night as I left work to make sure my weight wasn't making it bow badly and cause the gearbox issues I've been having.

[UnknownStuntm...]

Seems odd.
Just so you know, when you sit on the bike, the chain can go tighter. It can also go tighter when you go over a bump and the suspension tops out. Most bikes do this (but not all, depends on the geometry) including a Vanvan.

The ideal method for measuring chain slack is at three or more points around the chain. You do this in case a particular point has been stretched.

If your chain was too slack, you'd notice gearbox selection issues, and most likely a thump as you let the clutch out in the lower couple of gears. I don't think the Vv has a cush drive, so you'd definitely notice this.

If it was too tight, it'll have untightened itself by snapping.

Also worthy of note, the Vv has a notoriously underspecified chain. A popular mod is to swap it and the sprockets out for a heavier duty one.

Imma go ahead and recommend you get a local garage to do that for you, before deciding to change the gearbox etc.

[Iain.]

Okay.

You need 25mm of slack with suspension unloaded.

You had 30+mm of slack with the suspension fully loaded.

You are supposed to take this measurement when the bike has no load on the suspension as sitting on the bike tensions the chain.

With the suspension unloaded, at a guess thats going to work out at closer to double the amount of slack that is allowed as a maximum tolerance. If the sprockets are good, the chain hasn't snapped, and the chain was correctly tensioned it simply cannot come off without defying the laws of physics.

I strongly suspect you've been measuring it wrong, but by all means dissasemble the gearbox

[finchy95]

Oh definitely! I'm not able to replace the gearbox as they're pricey. So I'm going to try the oil change and clean the cover out and if that doesn't work as you've suggested I shall now try uprated sprockets, and it hasn't snapped (thank fuck) it's just slipped off the rear sprocket and possibly the front I'm not sure yet but it's definitely caught on something under the cover.

[finchy95]

Well I've just been measuring it in one place thinking that sitting on the bike would slacken the chain so apologies to everyone for my ignorance and stupidity. I'll try 25mm unladen and report back.

[UnknownStuntm...]

[finchy95]

Set the chain up at 25mm UNLADEN and measured it near the front sprocket top and bottom, in the middle top and bottom and near the rear sprocket top and bottom. Then five miles up the road the chain snapped and blew about six links everywhere including into both sprockets and the left hand arm. so it's gone to a garage. Hopefully it gets sorted if not I'm buying a Honda and being done with it.

[trevor saxe-coburg-gotha]

That *is* strange. I've still got the OEM chain on mine and it's done nearly 10k. Imo, on this bike, power is so low that chain tension isn't that crucial. I mean sure, it being too tight is absolutely not a good thing, and being too slack risks it jumping off a sprocket. But as long as there's a bit of play, and providing there are no serious tight spots where links have tired, *and* if the chain is kept clean and lubricated, the bike will go about its business without any trouble.

And this is despite the fact that the OEM chain is seen as absolute rubbish by many owners (and an item that requires immediate upgrade to a heavy duty DID job - hint; with proper cleaning and lubrication it most certainly does NOT). Having said that, the OEM chain IS thin and insubstantial. Adequate is the best that can be said. Secondly, there is no cush drive either - so in theory the chain and sprockets can work against each other in a way that they might not on a bike with rubbers in the carrier.

However, and to repeat - this is a bike that makes so little power that none of these things really matter. What might prove to be dangerous oversights with more powerful engines (e.g. incorrectly tensioned chain, or overly worn / unlubricated chain etc.) will in all probability be forgiven by the small 4t 125 that powers the vanvan.

Nevertheless, IF the bike is continuously ridden harshly by an unsmooth rider, and IF the chain is very poorly maintained, and IF the chain is cheap shit, and the sprockets cheap and rusty, THEN problems may well be encountered.

But none of this seems to be the case (although chain brand remains unknown). Therefore, if adequate chain and sprocket maintenance can be assumed, perhaps the issue really does lie with the transmission. If something is badly awry in that part of the engine's guts, I suppose drive to the front sprocket could be uneven, jerky and problematic enough to stress the chain out to the point of being flipped off the sprocket.

Keep us updated.
____________________
"Life is a sexually transmitted disease and the mortality rate is one hundred percent."

Mobylette Type 50 ---> Raleigh Grifter ---> Neval Minsk 125

[finchy95]

To my knowledge it was all standard suzuki parts, the chain and sprockets at least. it was all clean and not rusted, the underside of the cover was actually fucking gopping with road dirt and mud and crap but the sprocket itself looked (fairly) clean. So your guess is as good as mine. I'll just wait to hear back off the garage.

[UnknownStuntm...]

[finchy95]

Apparently the chain has fucked most of the ancillary parts, the arm and covers and such on the left hand side so it's been sold and I've got a brand new CBR 125 R that I'm picking up tomorrow, thanks to everyone that posted here for all your help!

[Iain.]

So after the chain came off and got mashed up..then you just put it back on without inspecting the damage or looking for tight links?

Perhaps it would be wise to ask a mechanic at the dealer how to adjust the chain as all of this seems to be down to poor maintinance/lack of knowledge.

[finchy95]

The chain wasn't mashed up I checked it all the way around. Alas it matters little as I'm getting a new bike.

[Iain.]

[UnknownStuntm...]

[Iain.]

[finchy95]

Obviously It's mad important to keep on top of the chain and everything! But what I meant is I don't have to worry about the van van and all its niggles. But I'm going to be super vigilant with the CBR and not letting it get into the state the van van was in.
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2005 suzuki van van - Sold. -> 2015 honda cbr 125 r - current bike.
Now's not the time for fear. That comes later.