Cbr900Rrn - No Power

[Arsix]

Hi all, recently finished rebuilding my 92 blade, was going to book it in for it's MOT but before that I thought I'd give it a run down the road to top up with fuel. Now when I started it up I did notice the rev counter didn't work for about 20 seconds, strange, anyway thought nothing more of it, now the bike idles fine and in neutral revs very nicely, no hesitation, but under load up to 5000rpm its a bit sluggish and above that it really struggles to the point where it just won't rev at all. I tested the fuel pump and it wasn't spinning up so I just bypassed it, but that hasn't solved the problem, the plugs are new, the carbs were stripped ultra sonically cleaned and balanced. It feels more like an electrical problem so I tested the coils, primary resistance is good, secondary resistance with no caps is bang on as well, but with the caps fitted the readings were high, one was very high so I changed them all for new ones from David Silver, no change. Anybody got any ideas why it only happens under load ? any suggestions would be greatly appreciated, I would really like to get this on the road before the good weather dissappears :-)

[jollygiant]

I would change the fuel pump as it pressurise the fuel and if there is no pressure there it would feel like no power, possibly?!?!

I may be wrong.

Edit to add that is a nice clean bike.

[Arsix]

I thought that as well, but after reading few a few fireblade forums it appeared that many people who had a buggered fuel pump simply connected the tank directly with no ill effects, apparently only the first few model blades ran a pump, no idea if that is correct. Anyway as it happens after a few beers the other night I had a look at the fuel pump, twatted it with a hammer and connected it to 12v and away it went, but as it turns out the fuel cut off relay is dead as well, and David Silver want £66 for a new one !!! I could refit the pump and bypass the relay and just fit a manual on/off switch if needed (not sure if it powers from the ignition switch or the kill switch), I just don't want to spend money replacing parts if its not going to fix the problem, fookin bikes :-(

[nigel.ted]

Does it black smoke when it gets to the point it wont rev?

Also does it fell like its flooding?

if it does, have you changed the air filter

[Arsix]

Nope no smoke, doesn't feel likes it's flooding either, filter is new, it just doesn't want to go, unless it's in neutral then it'll happily rev its nuts off, not tried leaving it in gear on a paddock stand though.

[nigel.ted]

id be checking the vacuum side of the carbs now trail and error process of elimination

had the carbs off my RF900 so many times

[CMSMJ1]

Does it not have a limp mode if the CDI cannot see the Speedo? SO, you got good fuses and all that shit? You said the rev counter was not instant - so a loose wire somehwere in the dash?

I reckon I am going to earn 20p with my tech skills...

[porter_jamie]

tank breather?

[nigel.ted]

Does it not have a limp mode if the CDI cannot see the Speedo? SO, you got good fuses and all that shit? You said the rev counter was not instant - so a loose wire somehwere in the dash?

I reckon I am going to earn 20p with my tech skills...

Its a 92 blade see the speedo cable

Does it happen straight away i.e if you pull off and give it some stick?

Or does it take a few miles to start playing up?

[CMSMJ1]

Its a 92 blade see the speedo cable

Does it happen straight away i.e if you pull off and give it some stick?

Or does it take a few miles to start playing up?

I know - but Hondas of that era* if you disconnect the wiring for the speedo then it has a limp mode at 5.5k revs..which sounds like this, n'est pas?

* as in my NC30 fo sho..but I reckon it is the same shizzle.

[nigel.ted]

* as in my NC30 fo sho..but I reckon it is the same shizzle.

Would that be if its a import for the speed restrictor?

[Alex_H]

If it's been sat long enough for the fuel pump to seize up, what's the inside of your float bowls look like now, could it have pumped some shit in? Or crap from the tank? I'd be going at it with biblical amounts of your finest carb cleaner just to double check. Then use carb cleaner around all the joints to make sure there's no air leaks (spray in area of carb/airbox rubbers, if revs rise, then air leak)

[CMSMJ1]

Would that be if its a import for the speed restrictor?

No, I reckon it is just a Honda thing.. A guess, but an educated one innit?

No restrictor on this moto but am sure the UK NC30s also have a 5.5k limp mode if the speedo wiring is disconnected, or if the dash fuses are gone, or if there is a bad earth

[Arsix]

Well if I had to put money on whether it felt like a fuel starvation problem or an electrical I'd say electrical, it does feel like a vehicle on limp mode (we have Citroen vans at work) but not sure whether a model this old would have such a feature. All the lights and switches work, the clutch switch doesn't seat securely and moves when you release the clutch, but thats just a cut off switch and shouldn't effect engine performance.

Tomorrow I'll whip the bodywork/tank off and check anything electrical, may also refit the fuel pump with a relay bypass switch. I'll have to make up some new fuel hoses though, the other ones were butchered to make a direct link to the tank via the filter

[Arsix]

If it's been sat long enough for the fuel pump to seize up, what's the inside of your float bowls look like now, could it have pumped some shit in? Or crap from the tank? I'd be going at it with biblical amounts of your finest carb cleaner just to double check. Then use carb cleaner around all the joints to make sure there's no air leaks (spray in area of carb/airbox rubbers, if revs rise, then air leak)

Everything checks out, the tank is clean, the fuel is fresh, fuel flow from the tap is good, the carbs are squeaky clean and balanced, as above if you start the bike warm it up and rev the engine while it's sat there you'd never know there was a problem

[Toneale]

Could be an HT lead breaking down under load or a plug cap. Also if you have the original coils on it they are now 21 years old and could also be an issue.

Regulator rectifiers are a known gremlin however you would more likely see melted wiring and a flat battery it can be easily checked with a multimeter and a haynes manual.

On the fuel pump front you can defo bypass the pump and connect direct to the tank on a gravity feed, (you are correct in saying the later 900's had no pump).

I know you said carb are pristine, however you could have a couple of blocked main jets which would explain why rev put 5k under load, might be worth checking whilst your under the tank.

Don't think the clocks wiring would be an issue given the speedo is cable driven and I have seen a few "low" mileage bikes that were being run with no cable. in fact i swapped my cable driven speedo for a later model one driven off the front sprocket with no ill effects.

Cracking scoot by the way.

[lorenzo]

Have you got another battery you could try on it? I've had this in the past with a couple of bikes that've been sat, it seems that although the spark's gutsy enough to do its thing when there's no load, and the battery's man enough to get the bike going, the engine feels very soft indeed without enough juice. If you've not got another battery, charge yours fully overnight then jump start it off a car or something, so that you've not drained it at all on the starter motor.

[BudgetBoy]

My bet would be electrical.(Weak spark under load)

Id start with a load test on the battery or use a KNOWN good one.

if its not that id test the stator.

To check it look for the 3 yellow or white wires all together. Unplug them, and turn the bike on. Go 1 to 2, 1 to 3 and 2 to 3 with your leads, and all of your results should be within about 25% of each other on VAC (volts alternating current). Next turn the bike off, and with the stator still unplugged, do an IB (insulation break) test on it. On Ohms, Each lead to ground. All should be OFL. If you get anything, then you probably have a bad stator. Next do an resistance test. Test all 3 like you did before (1-2,1-3,2-3), and you should get between .2 and 2.5 ohms for each. If you get one that is WAY WAY off in left field for any of the tests, then you probably have a bad stator

Hope that helps in some way.

Btw if your bike is flooding your plugs will tell you as they will be really sooty,pull one a out and see. But id stay with electrical.

[Toseland's Eyebrows]

Reg Rec? When the one on my 29 went it would start with the battery charged but really struggle / missfire if you tried to give it some gas.

It didn't melt any wiring, but it blew the main fuse when it went.

I ended up going with one from a R125 as CRM suggested, you have to swap a couple of wires around but they're cheaper than Honda ones and much more robust.

[Arsix]

Have you got another battery you could try on it? I've had this in the past with a couple of bikes that've been sat, it seems that although the spark's gutsy enough to do its thing when there's no load, and the battery's man enough to get the bike going, the engine feels very soft indeed without enough juice. If you've not got another battery, charge yours fully overnight then jump start it off a car or something, so that you've not drained it at all on the starter motor.

The battery is only a few months old and has no problems starting the engine, I plug it into the optimate if the engine hasn't ran for a couple of weeks, but so far hasn't given my any cause for concern.

[Arsix]

My bet would be electrical.(Weak spark under load)

Id start with a load test on the battery or use a KNOWN good one.

if its not that id test the stator.

To check it look for the 3 yellow or white wires all together. Unplug them, and turn the bike on. Go 1 to 2, 1 to 3 and 2 to 3 with your leads, and all of your results should be within about 25% of each other on VAC (volts alternating current). Next turn the bike off, and with the stator still unplugged, do an IB (insulation break) test on it. On Ohms, Each lead to ground. All should be OFL. If you get anything, then you probably have a bad stator. Next do an resistance test. Test all 3 like you did before (1-2,1-3,2-3), and you should get between .2 and 2.5 ohms for each. If you get one that is WAY WAY off in left field for any of the tests, then you probably have a bad stator

Hope that helps in some way.

Btw if your bike is flooding your plugs will tell you as they will be really sooty,pull one a out and see. But id stay with electrical.

Would that be the 3 yellow from the alternator as per the diagram, I'll do that tonight, I'm not 100% when it comes to electrickery, if you about later I may pick your brains further, if thats ok

[Arsix]

Reg Rec? When the one on my 29 went it would start with the battery charged but really struggle / missfire if you tried to give it some gas.

It didn't melt any wiring, but it blew the main fuse when it went.

I ended up going with one from a R125 as CRM suggested, you have to swap a couple of wires around but they're cheaper than Honda ones and much more robust.

Sounds plausible, I''l check the manual for a test procedure

[millerich]

I don't know if this is any help, but you mentioned a rev counter fault too. On Africa Twins of the same vintage I believe a dodgy CDI will often be accompanied by a rev counter issue too.

[BudgetBoy]

Would that be the 3 yellow from the alternator as per the diagram, I'll do that tonight, I'm not 100% when it comes to electrickery, if you about later I may pick your brains further, if thats ok

Yes correct mate.

i am about later until i go to bed 7pm.

[Arsix]

Cheers mate,

out of curiosity I've had a look through the photos I took when I stripped the bike down and came across this.

as you can see the wires to the right hand coil are the wrong way round from what the manual shows, would this have damaged the coil ? the ohms readings on the primary and secondary are fine with the new plug caps

[Arsix]

After a couple of hours in the shed I managed to check a few things mentioned above, first the stator, the connection is under the seat so it's easy to get at, measuring as described the readings are ok, next I disconnected the reg/rec and checked as per the manual, thought it was knackered but then realised the multimeter probes had to be reversed when checking between red/white and the three yellow and green and the three yellow, it checked out ok, next the reg/rec connector, there was a bit of crap in it which I cleaned out and the reading was a little high 0.6, the book says between 0.1 - 0.3. Also checked the pulse generator coil and thats ok. The only thing I noticed at this stage was what I assume was WD40 or similar on/in the stator connector probably from the rebuild, I cleaned this off with electrical cleaner.

So with that lot checked it was wheeled out put onto its paddock stand and fired up, I let it warm then put it into gear and holding the brake and covering the clutch increased revs and it seemed ok revved past 5k no problem

I then checked the battery and it was charging at 14.5 -14.7v, at this point I noticed this

This is the stator connector under the seat on the reg/rec side the wires are a little melted, one of the yellow wires looks like a brown, and, although I can't be sure, when I moved the connector the voltage to the battery dropped, although I may have touched the meter wires accidently, I double check that tomorrow.

So could the dodgy connection be causing my problems, and should it be possible to strip the wires back and clean and reuse the connector ?

[BudgetBoy]

Get that connection sorted mate..maybe chop the wires back and fit a new connection.. then see how it goes.. But that connection wont be helping matters for sure.

[phildawson8270]

if your battery is good, it should still run for quite a bit from the battery.

I ran a CBR600F from the battery (dead rec) for about 85 miles before it wouldn't restart the bike.

I'd be tempted to try new coils and leads, as said before, it may be that they're breaking down under load. I had a coil fail on my R6 all tests said it was fine, no misfires on bench testing either, but as soon as it was underload it played up no end around 6 to 7k

[Arsix]

SHIT ! sorted the wiring took it out for a ride, no change. Put the bike onto the paddock stand, into gear and revved past 5k no problem, then out onto the road and even going out of the estate you could tell it still wasn't right, out of the village wind it on on the fucking thing nearly dies, off the throttle and it comes back, so I tootled down the road and back again into the garden into neutral opens the throttle wide open, revs fine, WTF !!!!

Looks like I'll have to splash out on some new coils as a starting point

Tonight beer is my friend.

[Toneale]

Hey Arsix,

I believe I have some old coils that came off my RRN I also have a CDI unit off the same bike. Original Honda ones but they were working when I swapped them for some Dyna ones last winter.

All yours for £50 if your interested?