Help D:

[lewisweaver]

Hey all,

I was out on one of my little "ped trips" today (not drug related!) and something went wrong. I was cruising along happily at 30, bit of downhill so I opened her up. Then suddenly i heard like a weird noise from the barrel and the bike slowed down and cut out, as if i had applied the brakes quite hard. I kicked it once and it started straight again with no fuss. It was really quite bizarre! I have been looking on some websites and many things have led to either the ignition timing (ive had pre-ignition problems in the past), oversized jet (i jetted to 62 from 57.5 after putting on a 45mm big bore kit [as opposed to the usual 41mm]).

Does anyone have any idea if i've jetted it too high?

I do have a size 60 to hand.

Also, i have a dodgy oil pump, but it's still connected and only sometimes works. I am premixing aswell at a 2percent ratio.

Could someone tell me if it is bad for your engine having double mixture? and also would too much oil alter the performance (make it worse?)

Really appreciate your help experienced bike finatics!!

TYIA

Lewis

[TerraRoot]

it seized, only a small seize, that's why once it had cooled down it freed it self and started again. Amazing how much abuse a two stroke engine can take and still run, a slight knock on idle can be the entire big end long gone, it'll even run better for a while since you can get more compression with the piston smacking the head like that
62 jet sounds tiny, look at it this way as as rule of thumb:

50cc = 57.5mm jet (extra 15cc extra 7.5% main jet)
65cc = 69mm jet + 5-10 more for the expansion pipe, if it's working right.

Have you done a spark plug chop?

I love oil pumps, but i would not trust a dodgy one, sort another one or run premix, premix should be 5% (more if your using shite petrol station/lawn motor oil). More premix, less petrol going into the engine up jet by the amount of oil you have premixed.

[TerraRoot]

I just realised your bike is automatic, cvt right? when the engine blows on a cvt bike the clutch should just pull in, the engine dies, and your left free wheeling. belt, rollers, clutch springs start there. Highly sus that you felt as if the brakes had been applied.

[lewisweaver]

Aha yes it has 2 gears with 2 centrifugal clutches. When I was slowing down it seemed to be doing it in 2 stages. Almost as if changing down gears with the revs too high. Maybe I just out revved it because of the "racing" parts?

[TerraRoot]

so its a bit like a honda 50 so? how do you change gears? leaning a bit more towards engine seizing if it's not cvt.

btw did you chamfer the ports after you had it bored?

[lewisweaver]

Well it will automatically change gear when it hits 13mph. I'm unsure what you mean by chamfering the ports, but when I got the cylinder the ports where the same, if not smaller than the original cylinder. It appears to be exactly the same, bar the 4mm bigger. I have seized before when some weld got into the cylinder from the exhaust because I used that stupid gasless weld and some bits went into the exhaust. I think it may be the gears in the casing, so I think I'm going to change the oil, and see if that helps. I'll keep you up to date.

[TerraRoot]

should looks like this:

If their not done the sharp edge of the port heats up and then picks up on the piston.

[lewisweaver]

So if I use a sanding block dremel attatchment and grind off a 1mm 45 degree bit on the ports this will do the job?

[TerraRoot]

I use a small round file, it's quite easy with power tools to leave a lumpy edge which is nearly as bad as a non chamfered edge 1x45 is fine no more needed. Tell me what colour is your plug? it's an easy way of telling the mixture

[lewisweaver]

ah yes thats a good idea. The plug is black and oily. It seems to be fine but whenever i take it out it is moist and black. I recently cleaned my exhaust pipe by putting 50 odd ball bearings into the expansion chamber and shaking it with some petrol. Thick black gloopy sh*t poured out which leads me to think too much oil? I have tried several diagnostic websites to troubleshoot the plug, but it keeps leading me round in circles. Do you have any idea? Tyia

[TerraRoot]

black and oily is just that, too much oil and it's not getting burnt right. This totally mess's with the plug reading, i.e. you can't tell if it's rich or lean or just right until the oil delivery problem is sorted, Fingers crossed for you thats its not an expensive problem!