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Discussion Starter · #1 ·
Hi all.
Like Dewby, Wugga and others have experienced i have been putting up with the warm starting issues with my bike now for past few years to the point i have had to buy a second bike to get around on because i have lost that much faith in the cb1000r and I'm fed up of bump starting it :banghead.

over the years it has got worse and worse but this winter i decided on not using it and now the bike only fires up 50% of the time from cold and not at all when warm.
when it does decide to fire up it runs spot on until i kill the engine and go back to it.
I have tried putting the bike back to normal, resetting the ecu, tried replacing more parts then i care to count but nothing has seemed to fix the problem.
I've also been tempted to buy a second engine to see if that would fix the problem but i dont have the money to waste if it turned out electrical :confused:.

has anybody found out what the cause of it is yet and managed to get the problem sorted?
 

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It HAS to be electrical.-------Mechanical bits don't go bad and then cure themselves over and over again. They normally go BANG and then you replace them.

Don't know if our bikes are the same but all modern car ECU's record any intermittent fault in a memory which can be interrogated later.

Unlikely to be one injector cos it would fire now and then on the others.

Can you remove the ignition lead from one plug and stick a spare plug in cap where you can see it ?? If there's no spark at least you'll have a starting point to trace why no current is getting to the bike ignition.

The signal has to come from the ECU.

You say it fires up with a bump start. Does it do this EVERY time ???

With the key, nothing ???

Maybe at the same time the key spins the engine over it also, somehow, cuts the ignition. Starting it with a push bypasses this problem.

Hope some of this helps.
:thumbup
 

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Have you checked the valve clearances?
​A compression test would be a much easier option than trying to get at the valves.
 

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Discussion Starter · #5 ·
i checked the valves at 18k Eldon and I'm going to check them again this week to rule them out.

i will try those steps colvert as soon as possible, I've got the next week off and I'm determined to try and figure it out whilst i have the time.
unfortunately i haven't got a compression tester to check but I'm going to be checking the valves whilst i have it apart any way.
cheers for giving me a starting point to work from and any more advice is welcome :thumbup
 

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I know a lad who had an FZ750 a while back and from cold it would start fine. Hot it was a right pain. The differential thermal expansion of the metals removed the valve clearance once warmed and lifted it slightly off the seat. A bump start induced enough compression to always fire up and the power was fine so no giveaways there.
Colvert; a compression test may not show up the answer unless carried out with the engine at the right temperature range.

Only a thought and may not apply to your case.
 

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Discussion Starter · #8 ·
i should mention that it does fire up every time with a bump start.

its been tempting at times Mr nice haha, if it wasn't for the second bike i more than likely would of by now :lol
 

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Could be as simple as a small fuel leak? When hot/warm, the petrol evaporates quickly, so no signs of a leak?
Not sure if they have any vacuum hoses to do with fueling, but I know on cars these sometimes have a tiny split
in them which expands when hot...then the car wont start. Just a thought bab.
 

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Discussion Starter · #10 ·
cheers i will check that out as well :thumbup
 

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I too have this problem, in the 2 years I have had the bike it's had 2 batteries the latest a gel one, it's had a crankshaft sensor fitted it's had the ECU reset and been on Hondas laptop for diagnostics with no fault codes. The bike starts perfectly from cold but after say 2 miles to fill up it wouldn't start. I put the battery on an optimiser now and cross my fingers when I stop, the RAC man said it was charging the battery fine 14V when I called them out last time, but when you push the starter it sounds fine but it just doesn't fire, someone must know the answer
 

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I too have this problem, in the 2 years I have had the bike it's had 2 batteries the latest a gel one, it's had a crankshaft sensor fitted it's had the ECU reset and been on Hondas laptop for diagnostics with no fault codes. The bike starts perfectly from cold but after say 2 miles to fill up it wouldn't start. I put the battery on an optimiser now and cross my fingers when I stop, the RAC man said it was charging the battery fine 14V when I called them out last time, but when you push the starter it sounds fine but it just doesn't fire, someone must know the answer

If you push start yours when HOT does it start ??

Your bike and the OP's might have the same problem. A hot start with the BUTTON somehow cuts the current to the ignition. Spins over but won't fire.

If both your bikes start with a push when hot, the common factor is the starter button or the attached circuitry.
 

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My own bike seems to be voltage sensitive. If I check the battery voltage in the morning before trying to start the bike if the voltage is 12.2 or less volts the bike won't start. It WILL, however, spin over but NOT fire up.

If I put jump leads from my car on it it starts immediately.
 

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Discussion Starter · #15 ·
I too have this problem, in the 2 years I have had the bike it's had 2 batteries the latest a gel one, it's had a crankshaft sensor fitted it's had the ECU reset and been on Hondas laptop for diagnostics with no fault codes. The bike starts perfectly from cold but after say 2 miles to fill up it wouldn't start. I put the battery on an optimiser now and cross my fingers when I stop, the RAC man said it was charging the battery fine 14V when I called them out last time, but when you push the starter it sounds fine but it just doesn't fire, someone must know the answer

pm'd you back xaote :thumbup

Thats exactly how mine is wilf, i dread having to stop and put fuel in haha.
I've had 3 batteries in the past two years thinking i might just be really really unlucky with them.

my bike starts first bump when its warm colvert but thanks to bust knees i struggle to do that at times. its bad when my kickstart only xr is easier to fire up than the cb :notme.
I'm going to start stripping it and checking over everything tomorrow (if the new manual turns up) and I'm hoping to get my hands on a amp tester as well.
 

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Discussion Starter · #16 ·

My own bike seems to be voltage sensitive. If I check the battery voltage in the morning before trying to start the bike if the voltage is 12.2 or less volts the bike won't start. It WILL, however, spin over but NOT fire up.

If I put jump leads from my car on it it starts immediately.
that's one thing that's different colvert, I've tried jumping this of a van in the past when it hasn't wanted to start, tried with the van not running with no luck, running on idle with no luck and in the end i gave up, once it was cold though it fired back up fine.
 

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that's one thing that's different colvert, I've tried jumping this of a van in the past when it hasn't wanted to start, tried with the van not running with no luck, running on idle with no luck and in the end i gave up, once it was cold though it fired back up fine.

I'm a member of several car forums and a Mod on one of them. The fault you describe has been reported many times with cars that start when cold but won't when warm.

The fault has always been the cam/crank sensor which goes out of spec when warm so no signal is transmitted to the ECU. No signal means no start.

When the sensor cools the engine will fire up.
:thumbup
 
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Discussion Starter · #18 ·
yeah I've had the same thing happen to vans i have worked on and it is one of the parts that i replaced last year, it did sort of help when i replaced it but it was still hesitant to start(but it would after a few spins of the starter, it only had to be bumped a couple of times in a few month).
but the problem soon returned when the temperature started to drop again and then the bikes been away most of this winter.
 

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Like I said when I start from cold it fires no problem, it's if I stop within a couple of miles the thing plays up< if I take it for say 50 miles stop then start sometimes it fires first time others it take a couple of attempts. Thinking of buying a spare plug to see if there is a spark, Honda dealers have shrugged there shoulders and keep saying it's cos it's not a Yuasa battery, don't ring true. Not tried bumping it maybe find a hill lol I was just hoping someone may have had the problem and found the fix, desperation setting in
 

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yeah I've had the same thing happen to vans i have worked on and it is one of the parts that i replaced last year, it did sort of help when i replaced it but it was still hesitant to start(but it would after a few spins of the starter, it only had to be bumped a couple of times in a few month).
but the problem soon returned when the temperature started to drop again and then the bikes been away most of this winter.

On our bikes I don't know if there is any adjustment in the sensor position. Maybe even a little movement due to manufacturing tolerances but I do know the the position is quite critical to its operation.

With cars there is a lobe on the crankshaft or camshaft, depending on the sensor, which when it passes the sensor changes the current flow in it. This change is then relayed to the ECU which knows exactly when to fire the plugs.

If the sensor distance is just on the edge of being too far away it will now and then not send a signal. Sometimes ,when the engine is hot, the distance increases slightly through expansion and that's when the signal fails completely.
No signal= no start.

I have some info. somewhere on how these sensors work. I'll have to have a search to see if I can find it.




Colvert.
:thumbup
 
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