Engine cutting out...

[Joey23]

Having issues with the bike cutting out - it's been happening for a while - but has got worse since it's been wet the past week or so. Normally happens when the clutch is pulled in and rolling to a stop - but sometimes happens when in slow moving traffic - which is pretty scary...seems to be worse when the bike is warmed up. Anyone had similar issues? I've set the idle at 1750 but it doesn't seem to make much difference.

[Neosophist]

dont set the idle that high its supposed to be 1300, if it wont idle at that speed then something is wrong.

From the described symptoms and assuming everything else is ok it sounds like your bike is running rich somehwere. Start with the easy things first like is the choke sticking on anywhere?

[Joey23]

Thanks for the reply - it wont idle at 1300 for long...I'm a newcomer to all of this - sorry to ask - but what do you mean by 'choke sticking on'?

Joe

[speedy231278]

Each carb has a plunger on it that is operated when you pull the choke out. It may be that one/some/all of them are being prevented from closing properly when you put the choke back in. Most engines do not like running with the choke out once they have started warming up and will run rough or stall as a result.

[Neosophist]

Thanks for the reply - it wont idle at 1300 for long...I'm a newcomer to all of this - sorry to ask - but what do you mean by 'choke sticking on'?

Joe

if you dont know what a choke is then i suggest you find somebody to help you local that knows about these bikes. maybe there is a member on here?

A garage will cost an arm and a leg due to the amount of time it can take to do a service and overhaul on a compact v4..

old bikes esepcailly old abused 400s often need a good service and maintanance to keep on the road

[Joey23]

I understand what a choke is and in principle how it works - just didn't know that it may stick on rather than closing fully. A couple of members here have offered up some help so will get in touch. Supposedly bought the bike after it had been fully serviced and stripped / rebuilt - is something like this a common problem - or as you say a sign of an abused bike? Many thanks for your help. Joe

[Dynamohum]

Have the carbs ever been cleaned out could be blocked pilot jet giving you this problem, if it's been laid up at some point old fuel can gum up carbs giving poor running as you describe. Would get the carbs out and get the jets and tubes cleaned and checked using cammos guide first.

[Neosophist]

I understand what a choke is and in principle how it works - just didn't know that it may stick on rather than closing fully. A couple of members here have offered up some help so will get in touch. Supposedly bought the bike after it had been fully serviced and stripped / rebuilt - is something like this a common problem - or as you say a sign of an abused bike? Many thanks for your help. Joe

these bikes dont have many "common" problems. The most likely failure is a failed regulator causing the bike to under/overcharge.

The Honda unit is very small and doesn't react well with weak batteries, so long as you keep your battery fully charged and replace it before its too old to accept a decent charge even the stock reg/rec can last many years but most people have fitted heavier duty after-market units which can take more abuse.

The generator to regulator plug is also prone to melting due to corrision getting into it.

This is the only known weak point of the bike, anything else is down to poor maintanace / bad workmanship.

Most of these bikes have had hard-lives but its a good testament to how strong the engine is. Due to their age and unless they've had good money spent on them a lot of stock ones will have knackered / worn out suspension, worn bearings etc. Easy enough to sort but can be costly.

My bike hadnt been run in nearly 3 months until last weekend and it started after a couple of cranks and still runs like a watch, as they all should provided that everything is within spec.

For a bike that claims to have just been fully serviced and rebuilt you shouldnt be having issues like this.

[Joey23]

Hmmm - so it's had a new heavy duty reg/rec fitted as a precaution as after a couple days of ownership the generator failed - so replaced this and added a new battery too...starts every time now.

Little worried about the cutting out though...especially as she's my daily commute - need to try and get to the bottom of it asap - unfortunately noticing a pattern here with things going wrong.

[Neosophist]

Hmmm - so it's had a new heavy duty reg/rec fitted as a precaution as after a couple days of ownership the generator failed - so replaced this and added a new battery too...starts every time now.

Little worried about the cutting out though...especially as she's my daily commute - need to try and get to the bottom of it asap - unfortunately noticing a pattern here with things going wrong.

of course you will, its a 25 year old boy racer bike thats probably had a hard life and your trying to use it as an everyday commuter... these bikes were super popular in the 90s as they were a cheap fast sports bike, many young riders dont have the knowledge or money to maintain them properly, like buying an old Astra GTE or Golf GTi from the 80s.

while its certainly possible to use one everyday you should be prepared to replace a lot of stuff thats old and worn out, itll sure show up if your using it regularly. done it before with several old bikes, once theyve been rebuilt and youve sorted out any electrical issues theyll be just fine, but often hit your wallt more than you first think.

for example my last zxr400 was bought as a cheap but fairly decent looking 2nd hand 1992 bike.

However, after a month or so of owning it in order to get it into daily shape where i could just get on it and never have to think about "will it go from a to be" and just worry about general maintanance I had to.

* replace all bearings, wheels / head / swingarm
* new cam-chain / tensioner / head gaskets / re-grind and seat leaking valves and stem seals / re-adjust shims.
* new carbs and ecu and rebuild new carburettors with new o-rings, jets and gaskets throughout, replace inlet rubber mainfolds too
* rebuild fuel tap, fuel hoses.
* new chain / sprockets / tyres
* rebuild clutch
* rebuild forks with new seals and bushes
* rebuild brake calipers with new seals front and rear and new pads,
* new exhaust manifold gaksets.

After all this my wallet was about 900 quid lighter but I used it almost daily for a year without any issue apart from oil change and check / adjust cables etc, made 66hp on the dyno and handled like it was on rails, but did require a lot of effort to get there.


it sounds like your bike has been bodged along the way just to keep it on the road as they so often are due mostly to the cost to do something properly.

It doesnt sound like it was properly serviced and what not before you bought it, it shouldnt be cutting out at all, i wouldnt even risk riding a 400 that did until i found the issue, its NOT normal at all and depending what the cause it you might be making something worse.

Guy on here a while back bodged a big reg/rec on but didn tbother checking the genny or replacing the old knackered battery that probabyl killed off the original reg/rec, carried on riding it and the bike started over-charging, killed the ecu and then the repair was a new ecu, battery, reg/rec and genny.

If cutting out is caused by high voltage it will almost certainly kill something at soem point, most likely the ecu, if its due to a fuel hose / vaccum hose / tank breather you might get stranded somewhere and need a recovery.

if tis due to heat / tempature you might just kill the engine.

to be expected when buying an old bike, using them as a daily runner is the worst as most problems come out quicker so until youve basically rebuilt them it always feels like you have your hand in your pocket. dont be too put off though, its nice to ride a classic bike when there all sorted, just getting them there can take its time.

Get your cuttting out issue isolated and sorted pronto first, its not normal.