14 replies to this topic

[Grunta]

Any help appreciated.
 

Bike has no power inconsistently below 4k rpm, i.e it feels like an intermittent fuel or air blockage. It runs fine above 4k up to red line at 8.5k. Bike has done 10.5k km. Rides a bit like an RD350, but not as smooth! Engine seems to operate ok with no load

 

No warning lights

Starts ok may be a bit rough, but will idle ok.

TPS appears to operate normally (checked this morning, using diagnostic mode)

 

3 days ago I cleaned the fuel out of the tank and pulled the fuel pump apart - both were reasonably clean, carefully cleaned the fuel pump and reassembled. I thought the air intake flap was the problem so have disabled it.
 

Put it back together with fresh 95 RON fuel and rode 20km but still has the same prob.
 

Yesterday drained coolant, took the radiator off to get at spark plugs (?), which were fine - grey with no deposits. Removed the remains of a mud wasp nest next to the rocker cover air breather (couldn't see any damage, but may need to take apart again to look properly). Put back together and stalled it in the drive way re started ok, but no change. Hosed off engine while idling to remove any coolant - kept running.

 

The only other thought I had was cat convertor, although don't think it would run at high revs if this was the case .  Similarly the injectors.

 

Ta Grunta

[fixitsan]

Is the battery voltage good at low rpm ?
Possibly low output from alternator

[Grunta]

Thanks Fixitsam, 12.6 at start, 14.4 at idle so probably ok

[TDM4ever]

Did it use to run better below 4K, or did you get it like this?

 

If it used to run better, did the prolem suddenly appear? If so, did you do anything to the bike that might have caused the issue (e.g. changed/modified exhaust and/or airfilter)?

Edited by TDM4ever, 24 August 2017 - 11:34 am.

[JBX]

 

a mud wasp nest

 

Let's hope this is the result of the last winter storage...

Joke apart, check the airbox rubbers fit correctly on the throttle bodies - air tight.

Check other air hoses for any bird/snake/mouse nest...

[Grunta]

Thanks for the replies. Down here it was summer/autumn, but bike hadn't been ridden for a few months (started and let idle a couple of times).

 

The bike was completely standard until I disabled the the air intake flap a couple of days a go. The problem wasn't apparent before (I've owned it since new). I used to have problems with mud wasps blocking the carby vent on KLR250s that I've owned which created running problems, so that's why I suspect they've blocked something somewhere. Think I'll pull the mufflers off today and have a look

[Riggers]

A friend of mine had a very similar problem to this with his Guzzi V Twin. After months of investigation it turned out to be
be a very slightly damaged fuel line. The rubber pipe had a tiny nick in it caused by the clip holding the pipe to the pump.

The damaged pipe was allowing the pressure in the pipe to drop slightly causing the ECU to play havoc with the fueling. As
revs increased it seemed to sort itself out and ran ok above about 4k revs.

Might we worth a check. Good luck.

Riggers

[dicky1]

The symptons suggest the mixture might be too weak. Either too little fuel (a blockage or partial blockage in the fuel feed.) Alternatively too much air is getting in eg poor seal on air filter or no air filter)

[Catteeclan]

Haven't run the battery down and it's reset the co down to -128 on one cylinder?

[Grunta]

Thanks again everyone.

 

Battery has been low, CO2s are 14 & 16, so ok. Hinged tank back and took off air box - everything seemed ok/intact. Mufflers were as sooty as I would have expected, blew into both mufflers and they seemed to have similar back pressure. Put about 500ml of water in RH muffler to see if anything came out when I started it ~ only steam and some water from front drainhole.

 

Will keep trying and report back when its sorted

[Grunta]

SOLVED...

 

It was the salmon - sorry, spark plugs. The or one of the original Denso X24 plugs just suddenly developed a fault at 10.5k km replaced both with NGKs. Seems to be ok now...  "Never assume anything"

[TKH]

Whenever you get at the plugs it's always worth swapping them out. All the effort to get there and only ~£5 for a set.

[dapleb]

Well found grunty.

[fixitsan]

Good find

[Grunta]

Thanks for all the suggestions - plugs are about 10 GBP here... not that it matters that much but always interested in price comparisons