My 05 4rt has just started playing up. Been running fine then last weekend Ok for first couple of laps then on returning back up to the car park struggled to rev out eventually getting worse - sounds bit like running out of fuel or a choke being left on with a carb bike.

Stopped bike and started ok then gets worse again - seems ok in section for a while but not when riding back to start.

Changed plug, checked every connection, cleaned throttle body etc. Checked tappits and general look round during last the week. Stripped all fuel tank and ancillaries out -

Went out yesterday and still doing it.

Seems worse when ridding slowly up rock streams for 10 mins then when trying to ride off its worse. Flat out across a bit of moor seems fine especially if I stop the bike with kill button then restart and instantly not as bed.

I know Gizza5 had fuel pump issues but wondered if anybody else had similar.

Definitely seems heat related - also possibly fiddling with wires coming out of generator seems to induce a miss fire but not 100% convinced.

Was wondering if maybe loosing electrical output would cause electrical systems to run slow - fuel pump etc - Thoughts, comments welcome. Going to try a alternative fuel system (tank, injector pump- from a friends bike - when I ask him) which might help eliminate top end items.

Have you checked coil connections?Earth connections?

Fuel tank breather?

Have spent a few hours today replicating the fault (apologies to the neighbors) Takes a good 25 mins tick over- gentle riding round the garden/drive and wrapping everything in towels to build up the heat.

Then started trying to cool various items down once it started playing up Hose pipe and air line)

Swapped Throttle body back to a standard one but no real success.

I'm thinking maybe fuel pump as Gizza5 had.

Going to swap whole tank, injector assembly next.

Gday, do those bikes use a high pressure fuel filter? I would assume that they at least have a strainer over the fuel pickup. It'd be worth a look at those. If it has an inline filter, check it by blowing it out backwards (by mouth air pressure only) into a bottle so you can see what's in it. If it takes any effort to do this it needs a new one. Apart from that look very closely at all connectors for corrosion. Its rare but I have seen it happen before! It pays to use dielectric grease on them while they are apart to stop this in the future.

Cheers,

Stork

Alright James

Couple of questions

When the rough running begins does the bike smoke?

What colour is the plug,

Have you tried blink test with the Honda linkup tool?

Hope this helps, let me know.

Simon Lewis

Hi Simon

No smoke -plug light grey

Haven't tried blink test -looks bit complicated to me. Not sure if fault last long enough/consistent enough for this to show up.

Cheer

James

There is a fuel filter built into the fuel pump. Its a bit awkward to get at. You need to remove the pump and from memory its behind a screwed on plate at the bottom. For want of a better description it looks like a tea bag with a hole in. I don't think there is any reference to it in the manual.

Its awkward to clean as well. I just kept rinsing it in clean petrol. Hope this helps.

Scragg

Thanks - tried that. Tank looked clean when I took it out. Did not remove filter from the end of the pump as looked bonded on but wiped away any contamination from around the outside - didn't look too bad. Also emptied and blew out the metal canister filter on the output side of the pump.

Cheers

Jimmy

Did you check the temp sensor in the radiator, because if this fails the ECU is resetting and engine is running at low level.

Try fresh gas.

To keep you up to date - swapped tanks over with mates bike. Mine ran fine mates started missing when warm. Looks like new fuel pump required.

Thanks for everyones input.

To keep you up to date - swapped tanks over with mates bike. Mine ran fine mates started missing when warm. Looks like new fuel pump required.

Thanks for everyones input.

Thought it might be that and worth swapping with a friends to eliminate but unfortunately not, as I said mine went the same way...................get youyr wallet out they aint cheap!!!!

The filter is not sealed in I've had mine to bits. It's only small and would block easily. Before you go to the expense of a new pump it's got to be worth a try.

Another thought is I would guess Montesa would not have a bespoke fuel pump made. The fuel pump is a big heavy lump of metal for a trials bike. I bet there will be road bikes out there with a similar pump though I don't know which ones. You're local breaker might be able to help.

Scragg

Another thought is I would guess Montesa would not have a bespoke fuel pump made. The fuel pump is a big heavy lump of metal for a trials bike. I bet there will be road bikes out there with a similar pump though I don't know which ones. You're local breaker might be able to help.

Scragg

Road bikes have a fuelpump with much more flow and more pressure, i have searched a long time but couldn't find one. Perhaps somebody else knows something.