Re-assembly 60cc with port matched setup - Very low power

[DanielMaia]

[Lots of photos now!] Re-assembly 60cc -Low power [solved(base cyl. gasket leakage)]

Hi there guys,

My first motor, 60cc, has broken the piston rings, and i opened it up, installed new bearings SKF, polished and port matched the transfers ports, installed a new base cylinder gasket, a new head gasket, installed all with stock exhaust, and stock carburetor.

The thing is: the idle is near the perfect (not really perfect) but is very constant and smooth. The problem is very simple, a tremendous lost of power. In idle it revs more or less, but in the road (with shift kit installed), it has lots of LOW power. it doesnt bog, it doesnt die, but revs very very slowly, what you guys think?

My misture ratio is 5%.

Other thing, i think the engine is very very hot when i take a ride of 1 or 2km.. (430F i measured on spark plug)

Thank you,

Daniel Maia

 

[Norman]

some of the things that could be wrong. You might have changed the timing on the intake and exhaust ports. The gaskets you used may be the wrong thickness.
You said it had broke the rings did you replace the rings? And the piston?
If you run a little too much clearance on the piston to cylinder that will cause blow by and over heating. You could have not enough clearance on the ring end gap. That will cause binding and possible scoring of the cylinder and again over heating.
If your piston is a 2 ring groove piston and you try running only 1 ring that will also cause problems
another problem is you could be running it too lean. You might even have the fuel to oil mix too lean (not enough oil) for break in 20 to 1 or 32 to1 using non-synthetic oil. There is a number of thing that I listed that could be wrong and there is more that could be wrong as I could list a bunch more.
If only I could see and hear it first hand but I can't you live on the other side of the big pond.
You might want to take it apart and see if the engine is binding or scoring the cylinder wall or scoring the piston. could be a bearing has scored as well.
I can only suggest to you what to do and I could be all wrong .
could be you just need to increase the base gasket thickness to change the port timing.

 

[DanielMaia]

I have installed new piston and new 2 piston rings, new base gasket (original thickness) new head gasket. The cylinder is the same (it has a little surface scretches, but no big deal).

The only thing i changed it was the exhaust port, the transfers ports (the cylinder not changed), and nothing else..

I put a new seal on the clutch side too..

The working of the motor is completely 4 stroke. Only at climbing a big hill i heard a nice 2 stroke sound, but the power doesnt change at all..

 

[Norman]

Those little scratches could be killing it. They allow the burning gases to blow by the rings and piston causing excessive heat.
you said you modified the exhaust port? hope you only made it wider messing with the top or bottom will change the port timing.
Have you pulled the spark plug to see just what it looks like? oily? If so then your running it way rich.
need to do a wide open for a while if you can chop the ignition check to see what the spark plug looks like.

 

[DanielMaia]

Hmm, maybe i will take it apart, to see the cylinder, but its weird..

What are the symptoms when a motor needs a bigger carburetor?

This weekend i will take a long ride to see the colour of the spark plug

The exhaust i only polished it around, and i think i take 0.5mm on the top..

 

[Norman]

did your engine run good before all of the problems?
Do you have the carb needle set at the usual stock setting on the c-clip?
could be your carb isn't set properly.
One of the guys had a carb where it would idle good but would not rev up. He sent me the carb and it did the same thing on my bike I found that the needle was tapered wrong and it was only like 0.003 off on the taper I chucked the needle in my dremel and using 600 grit wet/dry sand paper , put the right taper on the needle. Plus a lot of measuring it with a mic against a known good needle. That is or can be a very sensitive needle and just a little too much or not enough taper can make the engine run either very well or terrible.
So you may want to look at the carb. I doubt if your carb is too small as long as its the carb that came with the engine, if you've put on a different carb then it could be too small or too large or even just not set up properly.

 

[DanielMaia]

I said that because i ported the 2 transfer ports in the "case" (im not remember the correct term). I mean, the 2 transfer ports on the engine (not the cylinder) was port matched and polished.

I think that is nothing wrong with the port matched because is only that: port matched.

Leaks, i think it dont have at all...installed with strong threads, with all new gaskets, and stuff like that.

Yes, you may be right, because this engine it lasts 2500km, never run so good (very very "leakage"(lots of air leaks, but my knowlage was not so good)) as my 66cc engine, it vibrates a lot...but even so, its very weird..

The needle, you saying the end of needle?

I will post a new topic here, with other problem i have.

 

[Norman]

the needle will need to be measured against a known good needle its whole length or taper.

 

[DanielMaia]

Hey Normam, took some photos!

 

[DanielMaia]

 

[DanielMaia]

(this photo is with the piston all in top)

 

[DanielMaia]

The port match & polish i did in transfer ports:

What you think?

 

[DanielMaia]

(piston all down - exhaust port)

 

[Norman]

From what I can see it don't look bad.
You probably need to change the spark plug, I don't know what your running for spark gap but try 0.020 to 0.017.
You may also try 32 to1 fuel mix. I looks a little oily and to me the plug looks a little oily and maybe a little cold you could try a hotter plug( only go 1 step hotter) or just a new plug with the gap I recommend.
You got some nice photos.

 

[DanielMaia]

Thank you Norman, and i can say it's problem solved

The gasket of base cylinder was leakage, installed 2x new gaskets, and it's near the 2 stroke sound i like

Did 56km/h (wheel measured mm by mm to put in the speedo - 2014mm) down a big road, i think its aproved

Thank you Norman for all, i will take more photos in a few days

 

[Venice Motor Bikes]

It's possible that the new piston could be slightly different from the original.
I tried to swap pistons once & found that they were totally different!

 

[DanielMaia]

This is the 60cc motor i talked on this thread,

YouTube - 60cc Motorized Bike w/ shift kit

What you think?

 

[Norman]

You could ride it around so we could see and hear it under power. Just blipping the throttle don't tell me much other than it runs.

 

[DanielMaia]

Yes, i'll make that

I have installed a new seal, at magneto side, and its a little better now, but the 4 stroke at low rpms its killing me

I think its the design of the head, its rubish...

High rpms it has a good sound..

 

[Norman]

if your running the stock carb and have problems at low rpm its probably the needle not being the right dia it needs to be thinner up by the c-clip grooves and it will take only a couple of thousands off of its dia. to fix. If you have a micrometer see how thick the needle is at the top middle and at the tip. If you have a couple laying around measure them too find one with the thinnest dia at the top and try it.
if your brave to fix the needle that is causing it to run rich. chuck the needle up in a drill and using wet/dry sand paper 320 to 600 grit lightly sand it in the top area of the needle don't mess with the lower part, then check the dia. once you have about 0.001 in inches not mm taken off,try it on the bike.