My friend has an 05 4rt which has recently developed a flat spot which caused the bike to cut out just at the wrong moment and has caused him to have a few major off's eg when applying a large amount of throttle at the bottom of a steep bank side from around half to full throttle the bike just totally baulks out, the local bike shop has tested the basics and he has cleaned the air filter and swapped the plug, I'm from a car back ground and if it was a car the first thing I would try would be a coil. Any ideas on we're to start looking would be a great help, thanks Luke

Had the same thing with mine back along , turned out to be the throttle body. We changed every thing from a spare bike and this was the last bit but it cured the problem.Not the easiest bikes to fault find on unless you can do what we did.Good luck !.

Yeah I have a 08 4rt so we can start swapping bits, how much did the throttle body cost you?

got a second hand one for £100 , worse thing that I ever did to the bike as it transformed it for the worse ,even the exaust note changed to more barkier and grip became very poor in mud. I have since sold the bike as I lost faith in it. Wish that I had bought the re programeable body so as i could have at least been able to soften things a bit.

hi my 07 had a similar fault it turned out to be the teabag filter on the bottom of the fuel pump ,i removed pump from fuel tank and cleaned filters with brake cleaner all ok now

As brokeit has said, look at the filter on the bottom of the fuel pump. Be careful though, as these are not replaceable, you have to buy the whole fuel pump if you damage the tea bag filter!

Pidcocks quite often sale brand new throttle bodies, off bikes that have had a programable throttle body fitted from new, on EBay. So keep a look out, I managed to get one for just

Edited December 15, 201213 yr by shedracer

Does this happen straight away or only after the bike has been running for a while? After bike starts to exhibt the problem does it get worse and worse as you keep riding? Does the bike then start and run fine for a short while prior to the problem returning? If yes to above then could well be the fuel sock. Had this condition occur on a couple of 4rts and initially change complete fuel pump assy which cured the problem. Second time I perservered with swapping and cleaning things and after a very thorough cleaning of the sock filter cured the problem. I found significant amounts of degreaser/carb cleaner and an air line did the job.

PS If it's not the sock and is the throttle body would suggest holding out for a PTB as makes the bike so much more tune-able

Does this happen straight away or only after the bike has been running for a while? After bike starts to exhibt the problem does it get worse and worse as you keep riding? Does the bike then start and run fine for a short while prior to the problem returning? If yes to above then could well be the fuel sock. Had this condition occur on a couple of 4rts and initially change complete fuel pump assy which cured the problem. Second time I perservered with swapping and cleaning things and after a very thorough cleaning of the sock filter cured the problem. I found significant amounts of degreaser/carb cleaner and an air line did the job.

PS If it's not the sock and is the throttle body would suggest holding out for a PTB as makes the bike so much more tune-able

Jimmyl, all the question you ask describe this fault really well, thanks everybody for your replies, il get him to drop it at my garage and check the sock filter, Iv had this on a Civic type r before we're instead of having a inline filter that can be changed on a service these are fitted on the tank pick up and get gummed up

Progress report next week, thanks Luke

I were once involved in finding a similar problem with a Honda 4Rt from 2005. The symptoms you described were exactly the same as on my 4RT. From half throttle to full throttle - the bike totally dies or misfire.

The bike starts as normal.

After a thorough check of the bike where i in the first place concentrated my self about everything electrical on the bike. I measured all the wiring from the throttlebody and to the different sensors and components on the bike. I also swapped the thottlebody without any change at all. I came to the conclusion that it must be a mechanical problem since everything electrical on the bike - is within the specification.

And now to the cause of the problem - it were the camshaft wheel, that had jumped a tooth so the timing were wrong !

I´m not saying - that it is the same as your problem, but it can´t hurt to check the timing marks on the flywheel and on the camshaft wheel.

I hope you get the problem solved - it´s more fun when it can take full throttle.

Hi sleazy p

Do you got any progress with your Honda 4RT regarding finding the cause of the problem.

Have you checked the sock filter in the tank as you mentioned !

Yeah did the sock filter, in the end it was a new throttle body that fixed it. The sock filter was well kankered up but made no difference when cleaned,