Minarelli 2T rings

[2strokd]

Checking the ex port is a GREAT idea :idea: !!!
Good one Brent! My uncles 55MPH Kymco slowed to a 30-35 MPH Kymco over a period of a couple weeks until the power was sooo low he wouldnt ride it. I thought maybe the top-end was just tired so i went to pull the top-end off for inspection. As soon as i pulled the exhaust i found the problem. From miles and miles of cheap oil being burnt through it(previous owner) the ex port had become almost plugged at the cylinder flange. I couldnt even get my pinky through.
After a good cleaning his scooter was right back on track and he was happy as could be ;D. Here are a few photos from that day.
I think this is it? If not it will kinda give you the idea as to how and were the can get "choked" full of carbon over time.
Before:


After a quick cleanup. You can take this a step further and polish the port to (as Brent mentioned) keep carbon from sticking as easy.

[duosport]

The exhaust port is totally clean. I checked the float height it is in spec and moves freely. The petcock works it shuts of when no vacuum and supplies fuel to the new fuel filter fine. Lines are good. No drag on the brakes.

How do I check the exhaust system for build up?

[stepthrutuner]

I would just blow through it to see if it feels restricted.

[duosport]

I have a Yamaha belt on the scooter. The part # is 3AA-17641-00. The size is not indicated. I went on line and looked up in a couple of charts and found that the Malaguti F15 requires a 757-17-28 belt size. When I looked up the Yamaha part I found the stock number listed when I searched for a Zuma belt. I found yet another chart that gave me the belt size for the Zuma as 738-18-28


It would appear that I have a Yamaha Zuma belt on my scooter with a slightly smaller circumference and originally a wider width. Now of course this belt is worn down almost too small in width. I guess my point is that the belt is not actually the correct size even before it was worn down.

[duosport]

Now I have found reference to a Zuma needing exactly the same size belt as my scooter 757 17 28. In fact I have seen different sizes listed as available for the F15. Seems there is a lot of misinformation out there floating around. Maybe the sizes they offer up are ok to use but it seems to me they are selling people off sizes.


This would appear to be the size of the belt that was installed previously on my F15. 738-16.5-28


www.martinracingdealer.com/SPD/pl-30210--80000CB5-1194360001.jsp

[duosport]

Gates belt size: 757 X 17 X 28 and some 4.0 gram roller weights on order.

[90GTVert]

Good luck. 20mm in length could surely make a difference if that's correct.

[duosport]

That link I provided shows the stock number of the belt and the actual length of it. that stock number is what is stamped on the belt put in my scoot. I would think that a 19 mm smaller belt that is also about at its recommended narrowest width before changing, would be a pretty big problem.


I will be holding the new one up against the old to see what is going on with the size.

[duosport]

I received the new belt and rollers today. However I worked late and did not get to it till late. I cleaned out the case and installed the new belt and rollers. Did not put the scooter together enough to test anything. I did however compare the new belt to the one that was on previously. It was noticeable larger in circumference.

[duosport]

Nothing improved.


New rings
new piston
Trued up the flat of cylinder
Cleaned carb. 5 times
New gaskets
new belt
new rollers

[90GTVert]

Did anything change? Not saying I don't believe you, but it's odd that a belt that much different in size would make no difference. I'd think you should either take off faster or top out faster, one or the other or both if the belt was too short before. :stumped:

Might be helpful to add things checked to your list to keep everyone on the same page. Off the top of my head, I remember :

Checked cylinder + ports
Checked exhaust for clogs
Checked intake and reeds
Checked fuel lines, filter, and petcock

Have you made sure the throttle cable is opening the carb all the way?

[duosport]

It had no power at take off or at higher speeds. It was slow. There was a difference. It was a little slower at all speeds. Not a lot but a little.

Cylinder and port was checked.

Exhaust was not checked

Intake and reeds were checked

fuel lines filter and petcock all functioning fine.

The "piston" in the carb makes full travel.

[duosport]

I have removed the exhaust. Now what?

[duosport]

The thing is very heavy. I looked up the shipping weights of exhaust pipes and I am seeing like 6 lbs. I weighed mine and it was 13 lbs. Granted there is a mount and a heat shield but it still seems very heavy to me. Perhaps it is full of carbon. I blew into the end and it flowed but not easily. I am not sure how easily it is supposed to flow.

How do I clean it?

[duosport]

So much to the annoyance of my neighbors, I rode the scooter with no exhaust. I figured if it was clogged there would be an improvement and there was. It was by no means fast but it was considerable faster. Now I am guessing that a proper exhaust on a 2 stroke would improve the performance over no exhaust pipe at all. Is that true?

So how do I clean out my exhaust pipe? I tried an electrical fish tape put it could not make the turns in the pipe.