Monkey / pit bike

[Marmalade]

I took my monkey bike out today. 125cc chinky engine that is fitted to most of these things.

It accelerates fine but nearing the top end of the revs it will be popping back through the carb, ease off a little and it clears.

Now after i'd done about 50 mile sat about 55mph I slowed for a roundabout and then it would only reach 40, stopped and there is smoke coming from the back of the engine, i've had a look and can't see a breather so assume it is coming from a leak in the crank case somewhere.

Let it cool for 15 mins, restarted and it did 50mph (my decision to go slower) for 10 miles or so without issue and no smoke.

there is no smoke from the exhaust so don't think it is the rings.

Any ideas? I'm of the mind of just buying a new 140cc stomp / lifan engine to bang in it so i'm not ragging the life out of it to cruise at 60.
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Nobby the Bastard: How yo tell the difference between the actual japanese and her just screaming because she's had live fish stuck up her arse? [url=https://www.nicks-shop.co.uk/bcf-goodies-15-c.aspGet BCF stickers and things here[/url] Reflective helmet stickers - Legal requirement in france - Clicky

[cb1rocket]

air filter fine? standard air box? It sounds like the faster you go the leaner its getting. My GP100 (yes its a 2 stroke I know) had the plugs missing to the carb cover and it was leaning out!

Carb clean?

Has this problem developed or was it always like this?
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Honda H100S2 Rebuild - https://www.bikechatforums.com/viewtopic.php?t=253852

[Marmalade]

[garth]

There is a crankcase breather at the back of the engine.

[Marmalade]

[P.]

Oil thins and creeps past rings/valve stem seals?

[Marmalade]

[P.]

So you get absolutely none from there? 100% sure?

[Marmalade]

[P.]

A quick google suggest blow by of combustion gases. But I'm sure you would be able to diagnose that quite simply?

[garth]

With regards to smoke on the overrun, nothing to worry about, every Lifan derived engine I've used after a long flat out session with smoke on a closed throttle slightly.

Crankcase pressure isn't a good thing! How much oil is in there, do you have a cooler fitted?

[Marmalade]

Smoky.
Looks like front of engine but its coming out the back of engine, under the tank and out the front of the bike.

https://youtu.be/U4oEAH5gxpk
____________________
Nobby the Bastard: How yo tell the difference between the actual japanese and her just screaming because she's had live fish stuck up her arse? [url=https://www.nicks-shop.co.uk/bcf-goodies-15-c.aspGet BCF stickers and things here[/url] Reflective helmet stickers - Legal requirement in france - Clicky

[cb1rocket]

Is the oil at the correct level? Seen video, how smokey! You can see oil on the offside. Where is that coming from?
____________________
Honda H100S2 Rebuild - https://www.bikechatforums.com/viewtopic.php?t=253852

[Marmalade]

[Marmalade]

Now, I feel an engine is in order and thinking an upgrade would be good.


If i sell it as is I'd be lucky to get £300 and then have to put £300 to it to buy another one so may as well spend the cash on an engine.

How about this one? https://www.ebay.co.uk/itm/261189495243?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

140cc stomp engine with all the bits.

Anyone have any experience of these engines or the company selling them?
____________________
Nobby the Bastard: How yo tell the difference between the actual japanese and her just screaming because she's had live fish stuck up her arse? [url=https://www.nicks-shop.co.uk/bcf-goodies-15-c.aspGet BCF stickers and things here[/url] Reflective helmet stickers - Legal requirement in france - Clicky

[P.]

Pretty sure binge advised I got one with that cam.

The Molkt is the bog standard carb, they recommend a Mikuni VM26.

I'd buy it if my Lifan shits itself Only issue is where to mount the cooler.

[Marmalade]

Sure I can bodge it on somewhere, i have duct tape and cable ties.
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Nobby the Bastard: How yo tell the difference between the actual japanese and her just screaming because she's had live fish stuck up her arse? [url=https://www.nicks-shop.co.uk/bcf-goodies-15-c.aspGet BCF stickers and things here[/url] Reflective helmet stickers - Legal requirement in france - Clicky

[P.]

[garth]

[mysterious_rider]

Oh dear. Looks like you have overfilled the oil. Look at that crap on the side of the engine!

Right, smoke is coming from the crank breather which is located just behind the top engine mount. look between those two pieces on the frame.

Right, time to check the oil level, what CC is it? If its only a 50cc they take a dribble of oil (seriously, I believe they take something like 300ml or less, my one ran on about half a cupful once)

If its a bigger engine I think average is about 750ml.

Don't bother measuring out anything, just look at the dipstick It'll tell you what you need to know..

Just fill it till it reaches the lower line. No doubt yours will seriously overread?
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KAWASAKIIIII

[mysterious_rider]

If its not the above then it could be shagged seals on the crank or something like that. Just nail the engine until you can afford a new one, also upgrade your sprockets! I believe I went 17-34 with my monkeybike. Possibly even 17-32.

You wont be able to sell your engine for much, IMO its probably worth a genuine £20. I bought a perfect 110 engine second hand for £30.

If you buy a 125, go for a lifan, they are damn near bullet proof. Or try the masai 125 engine, they even have proper heavy duty clutches!
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KAWASAKIIIII

[garth]

Every 50,70,85,89,107,124 or 140 I've had take roughly the same amount of oil. They're basically all the same crankcases, some (dependant on if they're semi-auto or manual) have different clutch cases, which allow them to take more oil, and some have oil coolers - but again, they don't hold a massive amount more.

Rough oil amount is 800ml - However OP said that he was half way up the level. My 140 with a cooler takes close to a litre.

I've never encountered any C90 derived engine taking as little as 300ml.

Either way, they don't take alot. Change it often.

[Marmalade]

Almost went well.

Engine got here in an oil stained box after dpd found it fitted in their van much better on its's side

Engine in, stator swapped, neutral light switch swaped, foot pegs swapped and exhaust bodged on, starts lovely, sounds nice but has no neutral.
I've not contacted them yet as the casual, Oh just pop the engine back to us by another shitty courier and we'll send you another one in a week after using god knows how many excuses to blame you for the fault.

so, spent most the day steadily and carefully putting it in, changing bits, making bits and getting it all sorted and i'm going to have to pull it out, send it back and them say "where is the clutch cable guide that was on the engine we sent you?" etc etc


Any suggestions as the the no neutral before I start my quest?
____________________
Nobby the Bastard: How yo tell the difference between the actual japanese and her just screaming because she's had live fish stuck up her arse? [url=https://www.nicks-shop.co.uk/bcf-goodies-15-c.aspGet BCF stickers and things here[/url] Reflective helmet stickers - Legal requirement in france - Clicky

[garth]

It wouldn't be the first time an engine has arrived with the shims on the gearbox shafts arranged in the wrong order.

P.s. Luckymx are £30 cheaper for a 140 engine.

[P.]

So tempted to get a 140... but I'll need to sort the brakes first, they are dire at best.