Bn125 wont start. May have hot seized.

My brothers bn125cut out going approx 50mph down a dual carriage way. He described it as losing power and then cut out.

When he tried to restart it the starter just clicked and bike did not turn over. 20 mins later starter turns the engine over but no start. (Only found this out later)

I arrive check there is fuel in tank, try turning the tap to prime. No difference.

Check spark with a spare plug and it's fine.

Take out plug and has spark, not as good as with test plug though. (Notice that plug is not wet with fuel)

Put finger over plug hole and there is compression. I was expecting more however I'm no expert on small engines though it did make my finger tip feel quite hot when turning the engine over. (Didnt really notice a smell of fuel during this)

Then I notice no oil showing on the sight glass even when tilted past upright. The oil and filter was changed with a genuine kawasaki one approx 3 weeks ago. There is no oil leaked from the engine and my brother tells me there has been no smoke so this is a mystery.

Another spanner in the works is that it had just had a cutting out issue after changing the clutch cable. This fixed itself after some fiddling and reinstalling the cable . Assumed the problem to be something to do with the cut out switch on the clutch as the bike would cut out when the clutch was released slightly in gear. Also, When changing the cable my brother had been lifting the clutch arm/shaft on the engine so he could turn it to get the cable in . Not a good idea imo but all seemed to be ok when put back together.

I dont really know where to start trouble shooting. The no oil and not turning over when hot make me think its seized, however it is now turning over fine and has some compression. (Will check with compression tester to be sure) . The plug being dry makes me think that there may be a fueling issue although I realise this may just be wishful thinking and still leaves the mystery of the missing oil and not turning over when hot after cutting out.

I haven't been able to have a good look at it due to the current travel restrictions and social distancing rules and I'm hoping someone more experienced can give their opinion on where to start so I am best prepared for going to try and sort it.

Any input is appreciated,

Thanks, Ian

I should add the bike is a kawasaki bn125, on a 56 plate

I used to have an 03 eliminator 125 which too hot seized very partially when I was riding it but I just let it cool down for 30 mins and it was ok afterwards (it had been singing its nuts off constantly for the preceding 3 hours of the journey)

As for fuelling it may have pulled through some crud and may just need the carb cleaning up.

As for no oil being visible when I got home from said ride and gave the engine a good going over I discovered the engine was being slightly starved of oil as there was a leaf and some other detritus in the sump so once I cleaned it out it seemed to perk it up some what once back on the road.

Where are you based?

Cheers rich

Hi rich. Thanks for the reply.

We are in wigan, greater manchester.

I am thinking about pulling the sump plug and seeing what comes out, filling it back up to level and then putting a drop of fuel down the plug hole.

How difficult is it to clean the sump out, do the cases need splitting?

From memory I believe it's the right hand engine casing needs to be removed and you will have access to an oil strainer behind some gauze mesh which might be all crudded up, should definitely drain the oil and see if theres any bits of metal swarf in which will indicate any other problems

I've downloaded a manual so will check it out. I've just spoke to my brother and he has put some oil in and it took about 3/4l. He says he can smell petrol when its turning over.

Have told him to drain the oil and let me know.

Also tell him to check the oil to see if it has fuel contamination as that would point to a problem with the rings.

I'd definitely remove the carb and clean it as due course given its easy to get to

I will do. Thanks for the help.

I'm going round tomorrow so will let you know how I get on.

Apparently the oil doesn't smell of petrol although he had diluted it with some fresh stuff and the bike has been stood for a few days now..

Cant find my compression tester so am just going to put it in gear and try pushing it to get a (very) rough idea for now.

Whilst it is drained of oil it makes sense to check the oil pick up screen first. Am going to check for fuel in the float bowl, the air filter to make sure it's not got wet and/or sucked into the carb. Re gap the spark plug and maybe try some fuel down the plug hole. Not getting my Hope's up but it will at least start to narrow it down and maybe give some clues.

I'd probably not suggest putting meat fuel in to the bore as it could just make the plug wet as it wont be a mist of fuel vapour and it may just leak past the rings if they are at all knackered.

First port of call should be gap the plug, check oil pickup for detritus and refill with required oil, then I'd check the air filter and check the carb out for shite that could be stopping fuel from getting to the intake.

As for testing the compression I'd just use the thumb over plug hole if you dont have a tester as trying to wheel it with it gear wont really tell you much

I have done the thumb over the plug hole thing and I dont really have much to compare it with. Yes it pushes my thumb off the hole but so does a bike pump. At least with putting it in gear I can gauge its resistance better as I know roughly how it should feel.

The drop of fuel down the plug will tell me if it is getting fuel or not, if it fires then spark and compression are ok. It's a pretty standard check.

The other things you mentioned will be checked also.

Will let you know how I get on.