Does bump starting damage anything?

[A_morti]

On my way into the work car park I have to stop on a downward ramp, reach into a pocket for a pass card, scan it, and then head under the barrier, ideally as quickly as possible.
I've taken to stopping the CBR 250 in second and using the engine to hold the bike, then letting it roll a few metres with the clutch in and start itself in second.
Is that a bad idea for any reasons I might not considered?

[wull]

Nope it’s absolutely fine and don’t let anyone tell you otherwise.

[Ian]

+1

I know it only had 3 moving parts but I used to bump my Bantam every time because it was a poor starter

[cheb]

The only engine I was ever told not to bump start was in my mk7 Transit. It was because the timing belt could jump as it was tensioned by the engine oil pressure, or so the reasoning went. I never had to so didn't worry about it.

[Skub]

Proper biker innit.

[Rockburner]

+1

I know it only had 3 moving parts but I used to bump my Bantam every time because it was a poor starter

IIRC our Bantam had so little compression that bump starting was harder than kicking simply because kicking it you could get the thing spinning a bit faster!

Unless of course I was diving down Remenham Hill...

[Bigjawa]

The only engine I was ever told not to bump start was in my mk7 Transit. It was because the timing belt could jump as it was tensioned by the engine oil pressure, or so the reasoning went. I never had to so didn't worry about it.

It's not great for clutch pressure plates as the wee straps that pull the actual face of the plate back can get kinked. Admittedly it's rare, but it happens. Doesn't apply to basket clutches on bikes though.

[Sadlonelygit]

The only engine I was ever told not to bump start was in my mk7 Transit. It was because the timing belt could jump as it was tensioned by the engine oil pressure, or so the reasoning went. I never had to so didn't worry about it.

What happens on a overnight cold start then?
Just questioning the rationale!

[Sadlonelygit]

Oh and yes bump starting does do damage!
Ruptured my calf muscle bumping a Fazer 1000

[cheb]

I asked that too. The response was that it was due to the suddenness of the spinning up speed, a cold start on the starter motor being slower and smoother.

It all had the whiff of internet truth about it, but as I say I never had to do it so didn't worry.

[porter_jamie]

You could argue it won't do a dmf any favours. But a fairly small engine like that the reverse torque isn't going to do much, and because it's a honda they will have tested the crap out of it. Don't drop it into gear when you are moving maybe you will be fine.

[Le_Fromage_Grande]

If you've got a catalytic converter bump starting will kill it because unburnt fuel gets caught in and then burns once it warms up, other than that you're good to go so long as you have enough power to run the fuel pump and injection.

[A_morti]

Oh and yes bump starting does do damage!
Ruptured my calf muscle bumping a Fazer 1000

Bit different than letting a 250 single roll down a hill !

[Whysub]

Battery went flat on my NC750. Live on a hill. Wouldn't bump start as it has a slipper clutch. Found that out trying its first bump.Knackered pushing it back home.

As for catalitic converters, how will a bump start kill them any more than spinning it over on the starter motor? 99% of bikes I have had to bump start have started as soon as the clutch engaged (disengaged?)?

[Mr. Dazzle]

As for catalitic converters, how will a bump start kill them any more than spinning it over on the starter motor? 99% of bikes I have had to bump start have started as soon as the clutch engaged (disengaged?)?

Plus the fact loads of brand new vehicles pop/crack/flame on the over run, a feature which is completely artificial and massaged in - the ECU just chucks loads of fuel into the engine when it's not needed, solely to make pops and farts in the exhaust This is in brand new vehicles with the most stringent emissions systems/cat designs.

The problem with unburnt fuel is that it doesn't remain unburned and causes the cat to overheat, as cheesy said. That's very unlikely to happen on an engine which is just starting, or even one that's been running for a while - you can see the cats glowing in some bikes! They get very hot anyway, the unburned fuel thing is only really a problem when it's happening continuously due to some other fault.

My (auto) car effectively kills the engine and bump starts it again all the time in normal driving. If you come off the pedal at speed it cuts all the fuel and sparks, so for all intents and purposes it's "off" even though it's spinning. When you put your foot down again it starts sending fuel and sparks again, so essentially you're bump starting it dozens/hundreds of times you drive it a reasonable distance.

[weeksy]

On my way into the work car park I have to stop on a downward ramp, reach into a pocket for a pass card, scan it, and then head under the barrier, ideally as quickly as possible.
I've taken to stopping the CBR 250 in second and using the engine to hold the bike, then letting it roll a few metres with the clutch in and start itself in second.
Is that a bad idea for any reasons I might not considered?

Can't you just use the rear brake ? Seems an absolutely bizarre solution to stopping.

[Taipan]

I would never bump start anything with a timing/cam belt...

[A_morti]

Can't you just use the rear brake ? Seems an absolutely bizarre solution to stopping.

From long habit I tend to keep keys in the left pocket so the pass goes in the right, and tends to get wadded up in the pocket from having my leg bent up rather than straight if I use the brake.
The rear brake on this bike isn't that great and it's quite a steep slope, so it takes a fair bit of pressure while the bike is already pointing down, it's not where your ankle wants to bend to.
So now I'm trying to get stuff out of a pocket that's wadded up, while remembering to keep the brake on hard enough, and balancing the bike left/right with the left foot while leaning right to the card reader.
So anyway, I'd rather have both feet planted, which means killing the engine in gear.
At that point the only question is starter, or let it roll.

[Buckaroo]

Can't you just use the rear brake ? Seems an absolutely bizarre solution to stopping.

From long habit I tend to keep keys in the left pocket so the pass goes in the right, and tends to get wadded up in the pocket from having my leg bent up rather than straight if I use the brake.
The rear brake on this bike isn't that great and it's quite a steep slope, so it takes a fair bit of pressure while the bike is already pointing down, it's not where your ankle wants to bend to.
So now I'm trying to get stuff out of a pocket that's wadded up, while remembering to keep the brake on hard enough, and balancing the bike left/right with the left foot while leaning right to the card reader.
So anyway, I'd rather have both feet planted, which means killing the engine in gear.
At that point the only question is starter, or let it roll.

Not sure if this would help, but I used to have similar problems getting into site past barriers. My pass/tag was in an arm strap, so I just lent over to the reader. Others had them strapped to their thigh and this worked well. Bit like ski pass holders from days gone by.

[Dodgy69]

Neutral, left hand on front brake, right hand with card.