Knocking and temp light

[2stroke]

Hello all, as you will know I bought my mk3 few days ago. I fettled with a bike over 2 days: cleaned the carb and tank, added inline fuel filter, serviced calipers, topped up the fluids, adjusted oil pump and generaly got accustomised with a bike (I am new to 2 strokes). Other half of my time I have spent reading forums ... One story especialy made impression on me: it was on some other forum, can't remember. The guy bought seized mk1, rebored 2 more times ,struggled a lot, spend lots of money and in the end, I think it was still fucked. Anyway... There are few things I need to sort it out: leaking forks, front wheel bearings...etc. I have to say,my bike looks to be in good original condition. 9500 miles. Been standing for 3-4 years with previous owner. So I have started the bike today for a second time, just idling and warming up- idling quite ok and I noticed 2 things: 1- there are some knocking /rumbling in the engine. not constant but regulary. Sounded quite low pitch. Obviously it's some bearings need replacing. But do you think its urgent or I can still ride it for a bit? And is it main bearings or can be something else? Do I need to strip the engine already? Bloody 2 strokes... 2- temperature light came on after 15 min so I switched it off quickly. What could that be? Frayed temp sensor wire or bigger things? So journey began... Thanks for your help
P.S. Bike started easily

[helisupp]

Hi 2stroke,

I thought long and hard about it and came up with only one real solution in my experience that fixes most mechanical things.

If you insert your credit card into the machine in the wall enough times and use what comes out, the fault will eventually go away.

[2stroke]

i cut my credit card long time ago... but yeah looks like that will be the only way out... BTW could you show me how to spend money wisely

I tried one more time. Let it cool down, started and after 15 min light came on. rad and cylinder very hot. I checked temp sensor - it's working good. Coolant in rad and overflow. Is it top end problem?

[helisupp]

1st step....... You will have to pull the thermostat and check its working ok.

[2stroke]

Hello Helisupp!
Do you mind explaining a bit more? Both radiators were hot when I touched it. I am off to find a cooling system picture.

[xstian81]

If the bike wasn't moving, its not that surprising the temp light came on after 15mins.. There are no fans on the radiators, and you need air flow through the radiators to regulate temperature.

As for the knocking, there are a number of things it could be.

If this is your 1st 2T, it maybe you are just not used to the noise they make. They are quite noisy when they are just idling. I wouldn't ride the bike if I thought there was a knackered bearing in the engine, it will only do more damage. Your best bet maybe just to take it to someone who has a bit more experience in 2T and see what they say.

[fallenmikethebike]

If the bike wasn't moving, its not that surprising the temp light came on after 15mins.. There are no fans on the radiators, and you need air flow through the radiators to regulate temperature.

As for the knocking, there are a number of things it could be.

If this is your 1st 2T, it maybe you are just not used to the noise they make. They are quite noisy when they are just idling. I wouldn't ride the bike if I thought there was a knackered bearing in the engine, it will only do more damage. Your best bet maybe just to take it to someone who has a bit more experience in 2T and see what they say.

+1 The best fix is to add a small magnetically driven computer fan, guess what, I have covered this at length on previous threads. Cost all of £10, plus a bit of time.
Noises, is the rumbling more pronounced on the downward cycle of RPM?
2T are noisy blighters and vibrate a lot, if you can still see objects in the mirrors, she should be fine.
Pop the magneto cover of, have a feel for any end float up and down, of which there should be very little, if alls well,give it a clean in there, check the drain hole in the bottom is clear, gently abrade the rust of the pick up points on the magneto, spray some ACF 50 about pop the cover back on.
If however, there is movement with a notable clonk, go and get a beer, you'll need it.
Mike

[2stroke]

Thanks guys!
I removed all cooling system apart the pump. What a great way to get to know the bike. Thermostat is definitely working thou little bypass hole was blocked, but that isn't important. Tomorrow will flush, clean and blow the rads and hoses. BTW some of the hoses and clamps are in a sorry state. Some old school hose clamps... Had a look on ebay for new hoses, but found only in USA. Where do you get a replacement cooling hoses in UK? Is it expensive? Must it be silicon?
Also, I unscrewed two thermostat housing bolts and realised they are head bolts too.I haven't touched other 4 or 3 on the head.On 4T you suppose to unscrew all bolts in a criss cross patern so not to warp head and so on. Do you think its gonna be ok? So I will fit everything tomorrow, put a new coolant and see if its the same.
Regarding overheating in 15 min I thought you suppose to warm up 2 stroke before riding. 15 doesnt seem much. 2T Vespas could idle for ages
Regarding knocking, I don't think it's right, I can hear it knocking sometimes loudly. Even some neglected 200K 4T courier bikes doesnot sound that bad. Thanks I will check the float.
Helisupp, whats the second step?

[twistednuts]

Vespas are air cooled with a big fan on the fly wheel so they can idle all day long.

Crms, like already mentioned, require air flow through radiator fins via bike movement, or Mikes fan. (Not a fan as in supporter - i dont think he has any )

[fallenmikethebike]

Vespas are air cooled with a big fan on the fly wheel so they can idle all day long.

Crms, like already mentioned, require air flow through radiator fins via bike movement, or Mikes fan. (Not a fan as in supporter - i dont think he has any )

Cheeky beggar.
The entire cooling system only holds a litre of water, as you have discovered it will quickly overheat with no airflow.
Fit a fan for trouble free use.
Do the bolts back up, no harm done.
Mike

[helisupp]

I think the temp light is normal after idling that long.

The knocking is not normal, I have several bikes from 2,000 to 20,000 miles and are all very quiet engines, in fact if you put a towel over the exhaust outlet all they do is whirr away quietly

The best diagnostic tool I have ever, ever bought is a mechanics stethoscope, used on everything from gas turbines to 2 strokes and could not live without it for diagnosing rattles, bearings, knocking etc, just a few quid on eBay.

Balance shaft would just be noisy and grumbling
Mains would be loud and rumbling
Power valve could knock ( hold with engine running to stop end float and see if any different)
Piston slap
Big end

Pulling the head and barrel off will find the problem.

Anybody else.

[2stroke]

Hey, thanks for replies!
Vespas do indeed have a fly wheel fan, forgot about that
I will fit a fan if no better tomorrow.
And thanks for stethoscope idea, i have it- just don't use it much. Not doing engine noise diagnostics very often. I will try poking it. Sounds like mains, not sure about balancer shaft noise.
I will keep you all updated.

[2stroke]

Hello all! Some news: put everything back, it's quite complicated cooling system: 2 rads, lots of hoses and very tight! And i thought some modern sports bikes are tight... Previous owner mixed hoses: tank return hose was connected to the carb and rad overflow hose went, i think, to the bottom of the rad. Fixed it and now not overheating but pissing coolant from both rads i think. How rare are they? Anyone got them for sale? Or can I recore it? Any experience? Cheers, guys!

[fallenmikethebike]

You can get yours repaired easily.
Mike

[2stroke]

Hi Mike, do you mind recommending anyone? What would it cost, do you know? Cheers, Paul