4rt problems

[peter_tenerife]

Hi guys, yes, I've got problems with a 4rt.

Recently bought off a good friend, I have a 2007 repsol with a 280cc kit on it.

It was going fine but sometimes very hard to start (and I have got the nak of starting 4rts). The last time she went I simply parked her up (letting her die out without using the kill button, not sure if this has anything to do with it?) and when I went to kick her over, the kick start would not go down. I pushed the bike back to the car and managed to loosen the kickstart, but on kicking it over, she made a funny sucking noise, as if the air was coming back out the air filter, signs of a timing problem?

So I took the head off last week to find the valves had touched the piston slightly, but the timing marks seemed to be right, although the mark on the flywheel was kind of between the T and the line.

Has anyone had this kind of problem?

The valves seem to be fine, I have to make sure yet, but seem to hold petrol in when poured on top.

Please help.

[honda_freak]

Hello Peter

I'm almost sure I have the same problem as you. My story starts with a brand new Honda

Montesa 4rt year 2008 which has been running less than 100 km. It is not my own Honda 4RT,

but a companion. He had come running in second gear with a few revs and suddenly the

engine stalled.

I have the task of finding out what is wrong with the motorcycle. I soon found that there is a

spark at the spark plug and while trying to start the bike with the kick starter, I can feel the

kick starter can not be depressed anymore. It was strange and I started getting a strange

feeling that something was very wrong here.

Sometimes I can take the kick starter down without engine just gets stuck. The next step was to

remove the valve cover and check the valve timing and, according to workshop manual crank

must be on the mark and the "T" and the two marks on the cam wheel should be level and

flush with the top edge of the cylinder head.

Valve timing was correct and I was about to pull the hair of myself because I was sure that it

was the piston and valves colliding. I took a visual check again and checked the valve chain

tensioner and cam chain if they were sitting right in relation to each other and they did. The

next thing I did was to remove the flywheel to get to the bottom Crankcase sprocket to exclude

any errors regarding valve timing and here I saw the error. The cam chain had jumped from the crank sprocket and was now firmly on the crankshaft with the result that the valve timing had shifted.

I then mounted cam chain correct on both crankshaft and camshaft wheel and the bike started

after a few kicks on the kick starter and it did not appear that the engine had been damaged.

So Peter_Tenerife - if I were you, I would double check valve timing again, just as a precaution.

It was a long story - but true.

I hope that you managed to find the error.

Greetings

Honda Freak

Denmark

Edited October 30, 2011 by Honda_Freak

[peter_tenerife]

Thank you very much for your reply. There are no signs that the chain had moved, but how could the chain come off the sprocket!? Surely the tensioner would prevent this from happening? Did your chain go back onto the sprocket itself or was it off when you opened the engine?

All 4 valves have touched the piston, making very little damage, so I think it must be timing, or maybe a sticking valve? but then that would only effect one valve?

I'm a bit lost as to what it could be.

[honda_freak]

I have no ideas how the cam chain has jumped the crankshaft sprocket. I will say that it is almost impossible, but it's the truth. It was only possible to detect after I had separated the engine.

If I can find the picture I took of the cam chain, I will upload it. The pictures were sent to the importer of Honda Montesa in Denmark as evidence of what had happened to the engine when the bike was brand new. Honda importer in Denmark had not heard that there would be some problems regarding the cam chain.

So Peter, I do not know if this helps you!