Chain Dilemna

[Dr Nick]

Today my chain decided to come off at 45mph, clicked down a gear and heard a crunch, then the speedo stopped working. Immediately pulled the clutch lever in and pulled over. The chain has wrapped itself around the sprocket a few times, ripping off the plastic cover that holds the speedo drive in. Hence it not working. Chain looks like it has managed to rip some metal off of the engine too and scar up my back wheel. Got a tow from my mate to his house about 5 miles away, no luck getting the sprocket off as we didn't have the right tools and didn't want to round the nut off.

Thinking about whether the gearbox could be damaged?, i'm going to order a chain and sprocket kit from bandcexpress tomorrow, Renthal hardened sprockets and an X ring 'racing' chain .

Was thinking about downgearing the bike while i'm at it. 1 down at the front and 3 up at the back?, i used 'Maurices Gearing program and it seems to be upgearing it . See Attachment


This bike seems to be a moneypit at the moment . Don't know whether to fix it all or just sell it as it is. What would you do in my situation .

Thanks in advance.
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[bikedudextrm]

Last time i was out on my bike the bolt that holds the front sprocket on came loose and the front sprocket fell off, stopped at traffic lights and went to pull away, nothing there just revving. Was annoying but a had bad feeling as i thought it was my gear box .
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https://www.bikepics.com/members/bikedudextrm/

[Dr Nick]

[Flip]

If it's a money pit, won't that be obvious when people come to veiw it? (does that make sense?) Run it in to the ground. Enjoy it Well thats what I would do.

[GSXR]

I don't know what's gping on with the gearing calculator thingy but if it's of interest I make the correct figures to be (to the nearest mph):

30 > 26
60 > 52
70 > 61
100 > 86
130 > 113
160 > 139

Overall reduction in gearing 13.33%
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GSXR | Ian
| 1991 GSX-R 1100M | 1994 XR600R | 1965 BSA C15T | 1970 Woman | 2001 Daughter | 1989 Leathers |

[Kickstart]

Hi

Check that the chain has not taken a chunk out of the engine, or damaged the swinging arm.

Chains coming off can be expensive.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Phoenix]

Ditto, where it managed to 'rip' some metal off the engine check it's not cracked the engine casing. This has happened to my VFR and the resulting damage (loss of two mounting points) now means I've got to drop the engine out to have it welded.

[Frost]

yup that gear ratio program appears to be borked
It appears to be calculating the gear ratio as:
rear sprocket / Front sprocket

where as it should be the other way around, hence when your putting in lower gearing its telling you your gearing up.

Attached is an excel spread sheet which i made to calculate the effects of upgearing on my bike. just pop in your ratios and it should calculate everything for you.

[EuropeanNC30R...]

The gearing program isn't borked, it's just not doing what you think it is. It calculates the bikes speedo error after changing the gearing. Eg in that screenshot your bike would be indicating 34.6 while you were actually doing 30mph. HTH

[Stew]

Mau, perhaps you should rewrite it so that it calculates new speeds (actual speed) after gearing changes rather than calculating speedo error after changing sprockets.
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"Unlike public school you don't need to have your arse up and your head down to go a long way...."

[zaknafien]

[Dr Nick]

Well after a bit of tugging and cursing, managed to get the chain and sprocket off, would itself up pretty tight.

Engine casing isn't damaged , just the casing that hold the speedo drive in has been smashed to bits. Don't think i'll bother downgearing the hornet for the time being. Where would you suggest to get Renthal CHain and Sprocket kits from .

Ordered an 020 today as it needs a new rear tyre and had the wheel off etc. £121 fitted. Is this a good price?
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[Kickstart]

Hi

Cheapest place I have found for chain and sprocket kits (although never bought any alloy sprockets) is Trade Direct.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Dr Nick]

[Kickstart]

Hi

No URL, but try phoning 08705 134859 .

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[rizo-sri200]

it happend on my dt125.
it cracked my engine casing where the clutch pushrod enters the crankcase and as a result my clutch return spring wouldnt do its job due there being no lug for it to latch too...

Cost me £65 to get a small lug welded to hold spring in place
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swift kick to the wing mirror puts em straight..
98' Bandit 600 with Slip on

[EuropeanNC30R...]

Try www.mauriceb.btinternet.co.uk/Sprockets.exe for an improved version of that gearing calculator.

[Dr Nick]

https://the-npf.com/stuff/ooo.JPG
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[EuropeanNC30R...]

Hmmm that's interesting one of the label's is slightly chopped on your monitor, it wasn't on both my 14.1" TFT and 17" CRT

[Dr Nick]

[EuropeanNC30R...]

When you get chance, could you try downloading it again from that location and see if it's fixed? (I'm looking at the 'e' in the 'Speedo Percentage error' label. Cheers.

[Dr Nick]

Yep, looks like you've sorted it .
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[Demonic69]

They both look the same to me
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Back on a Blade. Just feels so right.

[Dr Nick]

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