Engine won't start - backfires out the exhaust

[S2art]

Just got my full license and picked up a CRB400RR the other day. Now the bugger won't start.

I was told the battery is probably on its last legs and it hasn't been ridden for days and before that probably not regularly for ages.

It still turns over alright but just won't catch. I think I ended up flooding it by repeatedly opening up the trottle while cranking it - would this explain the backfiring?

I'm hoping it's just a weak battery, so really just looking for confirmation that it's quite normal for the starter motor to crank over but still not have enough juice to create a decent spark.

It was given 'B' service a year ago by Red Baron and has only done an additional 500km since then. Spark plugs etc all checked out fine going by the invoice. It's done 37000km so I'm hoping everything's not going to start falling a part now.

If I can't get it working, the wife's threatening to make me sell it, one of those I told you so arguements.

Any help greatly appreciated.

[Sam I Am]

have you tryed fresh fuel ? it does go off
do you know you can also jump start a bike with leads from a car........ both 12v

[TimeOut]

+1 for the fuel.

Are you using the choke?

[hayd3n]

change the fuel
dont forget to use the choke
also check your fuel filter it should be inline between carbs and fuel pump

[kwaka_crasher]

I was told the battery is probably on its last legs and it hasn't been ridden for days and before that probably not regularly for ages.

It still turns over alright but just won't catch.

Then it's not the battery.


I think I ended up flooding it by repeatedly opening up the trottle while cranking it - would this explain the backfiring?

Not with CV carbs. To start any flooded engine, full throttle and crank it.

I too would go with stale fuel. Bikes can be quite picky when it comes to this.

[quickbuck]

Righto,
Even though your invoice says it has New Plugs, well they aren't anymore.
You have wet them with fuel... And Stale fuel at that.

The easiest way is to take them out and clean them... Or, replace them with new ones, if you don't have a blasting cabinet.

Also drain all the old fuel out of the carb bowls and get some fresh stuff in there.
I've had to do this many times on various bikes... Even my trusty CBR600 when I left it sitting too long.

Now, I have posted the starting procedure for a 4-stroke motorcycle with electric start before, but here it is again:

1) Sit on Bike
2) Kick Stand Up
3) Turn on Key
4) Apply Full Choke
5) Pull in Clutch
6) Check bike is in Neutral
7) Press Starter (Note: I didn't say apply throttle), until engine fires but no longer than 10 seconds.
8) Wait for revs to climb above 2500-3000 before reducing Choke (Can let the clutch out in Neutral at this point too).
9) Ride off when engine is stable with no choke.

Note, all your gear should be fitted before starting your bike, but many take short cuts re this....

Hope this helps (and I thought of everything).

[S2art]

Thanks for the advice so far.

Well, tonight I only had time to siphon out the fuel tank and refilled with fresh. (Removed 8 liters, replaced with 10).

Following steps 1-7 above, she still doesn't start but the backfiring has stopped.

Previously if I applied the choke it would backfire, splutter, gurgle even more. Now, it doesn't seem to make much difference.

I'll have to wait until later in the week to drain the float bowl and check the plugs. Going but the Haynes manual it's suppose to be a "fairly easy" job for a beginner with some experience. We'll see, I guess we all have to start somewhere. At least it'll save time for the professional if I disassembly everything first :-)

I feel better pulling something a part that's already broken. Pissed off that it started on Saturday and not Sunday and I didn't touch it inbetween :-(

[quickbuck]

Yup,
Definitely Wet Plugs.

another trick is to remove the leads slightly, and then turn it over. It may fire up. Then you can put the leads back on fully.
Trouble is that is gives the CDI's hell, and wouldn't be the best for them.

So as not to take shortcuts, it is best to remove and clean things.

[CookMySock]

With all the plugs out, go full-throttle and no choke, and give the engine a three second spin-over on the starter - just to make sure theres no liquid in the cylinders.

Put the battery on the charger overnight, before you try and start it again.

Another thing that seems to help, is preheat the plugs. Put them in the oven at 150oC for an hour, and engines just seem to magically start up. Fit them and start it straight away. Full choke, no throttle.

Steve

[quickbuck]

Ummm, DB, why do that if there is "No Liquid in the Cylinders"?
AND if there IS liquid, you are asking for a FIRE!

So, don't be doing that.

[porky]

Excuse my ignorance but is it a crb or cbr. Secondly if it is running a cv carb my understanding is that its not a choke but an enricher. More fuel is added rather than air flow restricted to richen mixture. This then backs up the comments re hold throttle open and crank to clear a flooded engine. Dont blip the throttle as the accelerator pump will keep squirting juice in. Obviously you had this bike running before this minor set back, was it running like a sack of s@@t before you shut it down? When you do the clean out of the bowls do the jets as well.(2) If it has been sitting all sorts of crap (white powder) gets caked in the various galleries. Good luck.

[S2art]

Progress report...

Side fairings off, radiator swung forward, pulling the coil off the number 1 cylinder plug and bugger me if there's F all room in there to free it off. Shut the fuel off, loosened the clip around off the hose just after the on/off/res valve and bugger me if the hose won't come off. Out comes the fuel, off comes the bolt at the top of the tank. Half the tank under one arm, a little CRC and the hose comes off with only a little protest. (Bottom of the tank actually looks okay, hoping it hasn't sat around for too long). Off comes the air box, and I can actually see enough to free the coil through the hole in the rubber shroud. Only just managed to get the spark plug socket down over the plug, luckily it's still got the factory tool kit with it. The rest will have to wait until tomorrow night.

Porky - sorry, typo, should have been CBR400RR-N. It was actually running really well on the test ride. Started from cold without any problems and that was without the choke; this just over a week ago. Fingers crossed I don't have to touch the carbs... I'll try and start it after I've sorted the plugs - clean and dried or replaced.

Thanks again everyone.

[SS90]

Dont blip the throttle as the accelerator pump will keep squirting juice in.

CV carbs don't have accelerator pumps.

[SS90]

Progress report...

Side fairings off, radiator swung forward, pulling the coil off the number 1 cylinder plug and bugger me if there's F all room in there to free it off. Shut the fuel off, loosened the clip around off the hose just after the on/off/res valve and bugger me if the hose won't come off. Out comes the fuel, off comes the bolt at the top of the tank. Half the tank under one arm, a little CRC and the hose comes off with only a little protest. (Bottom of the tank actually looks okay, hoping it hasn't sat around for too long). Off comes the air box, and I can actually see enough to free the coil through the hole in the rubber shroud. Only just managed to get the spark plug socket down over the plug, luckily it's still got the factory tool kit with it. The rest will have to wait until tomorrow night.

Porky - sorry, typo, should have been CBR400RR-N. It was actually running really well on the test ride. Started from cold without any problems and that was without the choke; this just over a week ago. Fingers crossed I don't have to touch the carbs... I'll try and start it after I've sorted the plugs - clean and dried or replaced.

Thanks again everyone.

You are on the right track. The cause of your problems is certainly your plugs.

CBR's (all models 250,400,600) are particularly fussy on plugs.

I wouldn't recommend that you "cleaned the plugs", it's false economy.

In a short time they will become a problem again.

Gemerally, CBR models require a special plug, fortunately they are made by NGK, and easily available at most bike shops, but they are a special number, and as such, come with a special price.

Getting the plugs out will be a mission and a half (My first CBR400 was when I was 18 (14 years ago), and I think it took damned near an hour the first time.

The correct type of spark plug for your bike is a CR8EH-9 (the H is for honda, by the way)

From memory, the plugs can be as dear as $24 each, but they did go down in price a few years back. Hunt round.

There are alternatives, that are the same heat range etc, but have a different electrode, and therefore don't last well.

Many people use the cheaper CR8E plug, and, generally they foul on cold starts. (experience here)
This could be the cause of your problem.

Perhaps th eold owner has fitted CR8E plugs?

Also make sure the battery is a YTX-7L-BS, many stingy owners fit cheaper, non maintainance free batteries, and they simply lack the grunt to turn the engine over, and, at the same time, supply the needed 12v to the ignition system.

As a test, completely charge the battery, fit the new plugs etc (reassemble the bike) and put a volt meter across the terminals and see how many volts you get when cranking.....less than 10, then you also have a battery problem, which could be adding to your woes.

Tell you wife to calm down...they are great bikes!

[kwaka_crasher]

The correct type of spark plug for your bike is a CR8EH-9 (the H is for honda, by the way)

I hope you're taking the piss... EH means it's only a partial thread (1/2" of thread on a 3/4" reach plug) as opposed to just E which means it's a fully threaded 3/4" total thread reach.

[CookMySock]

Ummm, DB, why do that if there is "No Liquid in the Cylinders"?
AND if there IS liquid, you are asking for a FIRE!

So, don't be doing that.No you do that to clear the cylinders. It's completely trivial to disable the ignition.

Steve

[SS90]

I hope you're taking the piss... EH means it's only a partial thread (1/2" of thread on a 3/4" reach plug) as opposed to just E which means it's a fully threaded 3/4" total thread reach.

Yea, I was taking the piss, I meant to say the E stands for expensive, the the H for honda, but forgot where I was at when I wrote that!

[SS90]

No you do that to clear the cylinders. It's completely trivial to disable the ignition.

Steve

Sorry Steve, on this you are mistaken.

It is most certainly not "trivial" to disable the ignition.

I was a motorcycle mechanic for 13 years, and twice I saw small (thankfully) fires started by (experienced) mechaincs doing exactly that.

also, if the plugs are not earthed, and the ignition is operated, you can very easily destroy a coil, or even a CDI.

It' been done!

[CookMySock]

I was a motorcycle mechanic for 13 years, and twice I saw small (thankfully) fires started by (experienced) mechaincs doing exactly that.

It' been done!Yup, and I have done it myself. Why not pull the plug off the ignition pickup?

Steve

[SS90]

Yup, and I have done it myself. Why not pull the plug off the ignition pickup?

Steve

Erm, but that is "disabling the ignition system......."

[quickbuck]

Erm, but that is "disabling the ignition system......."

Well, not exactly.... There is still a chance that the spark will jump from the end of the lead to the engine.
Yes, I've seen it done by experienced mechanics too! And almost saw a YZ250 get absolutely toasted.

Admittedly the whole engine was fill of fuel, but fact remains, it only takes a vapour of the correct fuel/ air ratio with a high energy spark at the right time to start the fire.
Murphy says it will happen when you least want it to. Especially after trying to get if to work under the correct conditions... ie internally!

[kwaka_crasher]

Yup, and I have done it myself. Why not pull the plug off the ignition pickup?

How would that not be classed as disabling the ignition?

[CookMySock]

How would that not be classed as disabling the ignition?LOL who gives a fuck. Ya just want the fucker to stop sparking somehow so it doesn't ignite the fuckin flammable shit that is spewing everywhere. If ya can't shut down the high-tension site, ya shuts down the fuckin LOW tension side. :laugh:

Fuck me, all this rocket science is too technical for me... UN PLUG THE FUCKAHHHHH...

Steve

[kwaka_crasher]

LOL who gives a fuck. Ya just want the fucker to stop sparking somehow so it doesn't ignite the fuckin flammable shit that is spewing everywhere. If ya can't shut down the high-tension site, ya shuts down the fuckin LOW tension side. :laugh:

Fuck me, all this rocket science is too technical for me... UN PLUG THE FUCKAHHHHH...

Dude! You're the one that said it was trivial! :rofl:

[SS90]

Well, not exactly.... There is still a chance that the spark will jump from the end of the lead to the engine.
Yes, I've seen it done by experienced mechanics too! And almost saw a YZ250 get absolutely toasted.

Admittedly the whole engine was fill of fuel, but fact remains, it only takes a vapour of the correct fuel/ air ratio with a high energy spark at the right time to start the fire.
Murphy says it will happen when you least want it to. Especially after trying to get if to work under the correct conditions... ie internally!

Erm, what do you mean quickbuck?

Disconnecting the pickup lead will completley stop any spark happening whatsoever.

Think about it.

If the pickup lead is disconnected, the coil can't fire.

[gsx83esd]

take it to the bike shop and let them fix it , no hassles !( and i aint no L plate rider!)

[meowmix]

Just about CV carb comments thus far. What? I have CV carbs with accelerator pumps and the choke closes the vacuum slide.. Unless Keihin (I assume those are on the Honda) are vastly different to Mikuni.
I agree with the charging the battery and getting some fresh plugs. Seems strange that it worked for the test ride fine from cold with no choke. Personally, it sounds a little rich (like the air filter is a little clogged).

[SS90]

Just about CV carb comments thus far. What? I have CV carbs with accelerator pumps and the choke closes the vacuum slide..

So, when you open the throttle, little jets of fuel squirt into the cylinders, even when the engine is switched off?

[SS90]

Just about CV carb comments thus far. What? I have CV carbs with accelerator pumps and the choke closes the vacuum slide..

So, when you open the throttle, little jets of fuel squirt into the cylinders, even when the engine is switched off?

[kwaka_crasher]

Just about CV carb comments thus far. What? I have CV carbs with accelerator pumps and the choke closes the vacuum slide.. Unless Keihin (I assume those are on the Honda) are vastly different to Mikuni.

They are vastly different.


So, when you open the throttle, little jets of fuel squirt into the cylinders, even when the engine is switched off?

Yes. I'd actualy forgotten about this myself. I mean, who fuck uses Keihins! :lol:


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[S2art]

Another update...if anyone's interested...

Just for the record I chose not to crank it with the plugs out to clear the cylinders. I turned the fuel valve off the other day and cranked it before and after work... hoped it would shift any left over fuel into the exhaust. You'll probably tell me it was all for naught as there's still fuel in the bowl.

Anyway, plugs came out and replaced them all. This way if it still doesn't start I can atleast rule the plugs out and look at the carbs. The plug for cylinder 1 wasn't visibly wet although it had a definite fuel smell. Plugs 2 - 3- 4 all had fuel residue around the edge. The actual condition and colour of the electrodes looked fine I think - no build-up, no signs of wear, however they were more black than brown. Also gave the air filter a clean while it was out, but it wasn't exactly dirty.

Managed to get it all re-assembled with no leftover bits. Went to start it and I swear it caught for a second straight away. After a few more cranks I realised I'd forgotten to turn the fuel and choke on. After a few more cranks the battery was starting to go so I stopped there and it's on the charger overnight. Thinking about it there's only a small mount of fuel left in the tank and it's bound to be in the reserve level, so I'm feeling confident with a freshly charged battery and more fuel she should hopefully start.

Fingers crossed for tomorrow night. Thanks again everyone.

[SS90]

They are vastly different.



Yes. I'd actualy forgotten about this myself. I mean, who fuck uses Keihins! :lol:




shouldn't that be who the fuck uses Kymco?:blink:

Never seen that on a multi before, or have I missed something?

[meowmix]

Sounds positive!

And yep, the accelerator pumps are actuated with the throttle butterfly and squirt fuel as much as you can twist. Just a note, my carbs are only 5 years old, and I didn't spot any on some mikunis from '81, maybe its a recent thing? [/hijack]

[quickbuck]

Erm, what do you mean quickbuck?

Disconnecting the pickup lead will completley stop any spark happening whatsoever.

Think about it.

If the pickup lead is disconnected, the coil can't fire.

Sorry,
I read PLUG and got confused.
A better word would be connector.

But remember there is electrons coming out of that connector too.... potentially.

But, yes, that would all but disable the ignition.

[S2art]

Thanks everyone, she's up and running again... phew.

[Sam I Am]

fingers crossed for ya tomorrow

[SS90]

Sorry,
I read PLUG and got confused.
A better word would be connector.

But remember there is electrons coming out of that connector too.... potentially.


But, yes, that would all but disable the ignition.

It's ok, I see you are in Bulls.....Don't worry, I spent the first 5 years of my life there.... I get confused easy too!:blink:

I wouldn't sweat too much about the voltage coming out of a trigger pulse wire, about 0.5amps......

[imdying]

It would have gone without taking the plugs out etc... they're too often blamed and not nearly as trouble prone as people make out.

Carb'd CBRs, like a lot of bikes of that era, require a specific method for starting them... most un Honda, but that's the way it is. The fresher the bike, the less picky they are, but still somewhat funny.

Once you've owned that bike for a while, you'll know exactly what to do to start it first time every time; more importantly what not to do. Those CBRs seem to be pretty picky about how much gas you give them when cranking, i.e. don't even think about touching the throttle.

Of course, problem is, once you've upset it, that's it, they need to sit a little before they'll go.

The best ways to combat this are:
- Keep it tuned up
- Learn the 'trick'
- Keep the battery fully charged

As they get older, they tend to get sensitive to poor condition batteries. Having said all that, kept well tuned and having spent some months with it, you'll probably only have trouble once in a blue moon.

There is a danger of arcing a plug and setting the bike on fire turning it over with the plugs out. However you should be able to see, given how hard it is to get even your working assembled motor designed to do nothing else to fire, that it's a pretty small possibility.

[quickbuck]

i.e. don't even think about touching the throttle.



I have been told not to bother on any bike... by some wise man who has cleaned many sets of plugs...... ;)