annoying over rev

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scooterslag
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Sun Sep 06, 2015 12:41 am

Ok this is starting to get on my nerves,I've got a standard SX150 and for some mad reason it seems to over rev on the flat like a screaming banshee. It's not the clutch, it pulls like a train up hill in 4th but on the flat it's a different matter. I've inspected the clutch, sprockets, chain adjustment and cush drive and all good ( I made sure that I didn't have a series1 spring in the crush drive/front sprocket set up) the one area I haven't looked at is the gearbox- could worn bearings / cogs cause this? It seems to be working ok. Had the engine on the road for the last eight years but in the last couple it hasn't been running well, been slowly working my way around the engine, it's like it's been under-geared, any idea's? Paul
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Daggs
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Sun Sep 06, 2015 8:38 am

My first thought is air-leak causing lean running (which tends to be fast running, until the bang!)

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scooterslag
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Sun Sep 06, 2015 11:20 am

Daggs wrote:My first thought is air-leak causing lean running (which tends to be fast running, until the bang!)
Nope, engine running fine, text book plug chops, this is more transmission related, it gets into 4th then over revs where it used to storm away, clutch is fine by the way, had it in bits and all components check out fine
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bristolmod
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Sun Sep 06, 2015 11:49 am

so when it happens the engine speed has no relation to road speed? Is it appearing that the clutch is slipping although you are sure it isn't?

Chris
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scooterslag
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Sun Sep 06, 2015 12:18 pm

bristolmod wrote:so when it happens the engine speed has no relation to road speed? Is it appearing that the clutch is slipping although you are sure it isn't?

Chris
Hello Chris, yes the rev's don't match the road speed but the clutch is fine, no slip on pull off, it flies up hills in 4th and all the components (corks, springs,basket,steels) are all A1. Thinking it could be the cush drive though had that apart and all seemed ok, maybe I've missed something? Paul
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bristolmod
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Sun Sep 06, 2015 12:32 pm

Weird!

there was a case on here a while back where the cush "ramps" were worn and the spring also weak (albeit it was the correct size) Those combined faults caused the ramps to "overrun" each other giving the symptom you describe.

Have you done a straight swap of the cush bits for another set up?

If you get stuck I've probably got a complete cush and spring in the spares box which you are welcome to for the postage cost.

Actually- I will be down in your area (West Down) in the next few days- are you the guy near Braunton that I bought a rear mudguard off a while back?

Chris
Scootering since 1968.

phil23fair
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Sun Sep 06, 2015 12:37 pm

I had a similar problem some time back. It turned out to be a worn front drive sprocket

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scooterslag
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Sun Sep 06, 2015 12:50 pm

bristolmod wrote:Weird!

there was a case on here a while back where the cush "ramps" were worn and the spring also weak (albeit it was the correct size) Those combined faults caused the ramps to "overrun" each other giving the symptom you describe.

Have you done a straight swap of the cush bits for another set up?

If you get stuck I've probably got a complete cush and spring in the spares box which you are welcome to for the postage cost.

Actually- I will be down in your area (West Down) in the next few days- are you the guy near Braunton that I bought a rear mudguard off a while back?

Chris
Hello Chris, nope I'm not the bloke with the rear mudguard though I remember buying a NOS 6v coil off you a number of years ago. Yes I'll take the cush drive set up off you thanks, I replaced the top hat off the cush drive as there was some wear but everything else looked fine, yes its surely is strange. Paul
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scooterslag
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Sun Sep 06, 2015 12:51 pm

phil23fair wrote:I had a similar problem some time back. It turned out to be a worn front drive sprocket
Yes I'm thinking something in the cush drive/sprocket department is amiss
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bristolmod
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Sun Sep 06, 2015 12:55 pm

what do you want to do? I may be in N Devon this week after Tuesday (depends when John Lewis get their finger out and let me know when my furniture is ready), or failing that it will be the following week. Whereabouts are you?
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