Yamaha...DT360A help needed

[kmac]

Buddy has a pretty clean, green, 1974 Yami DT 360 A...It had sat for a year or 2 and was all gummed up. He has no clue mechanically so I offered to help him out. I pulled the carb and soaked it over night in McKays carb cleaner bucket. I gently cleaned all ports and venturies and jets with a thin piece of copper wire and carb cleaner spray and air.

All blew clear and clean so I installed it back on the bike, kicked, kicked some more, the finally-kicked some more...lol, and after the cylinder and bottom end finally cleared out and the fuel circulated the motor she fired right up. After that she literally fired up 1st kick every time...way cool for a never tore down or rebuilt 40 yr old scooter.

One issue though...it does not rev to full RPMs. It revs clean and smooth from idle to about 3500 but then goes dead flat. It idles perfectly, crisp of idle throttle response, but flat at mid R's. It should rev to 6000 R's but won't.

Any ideas?
I am going to check the reeds, I failed to do that while I had the carb off...duh. It may be a broken or gummed shut reed. I also intend to check the auto decompressor on the front of the cylinder to see if it is stuck open a bit since it does kick start fairly easily compared to my memory of 360 beast back in the 70's.

Other than those ideas do any of you folks have ideas as to where I should look? ::022::

 

[eemsreno]

kmac
Try removing the air filter to see if its air restricted
That is a side mounted main jet on that carb so did you replace the o ring #214-14147 that is a must!

I had to go in a hurry --- back again.

With that being a side mounted main jet that means there is a fuel passage in the bottom of the float bowl, very easy to overlook that being plugged up.

Hope you get that old girl going good. that is a cool bike.

 

[kmac]

Yes, I took the boot off to see if there was a blockage and no change, I also covered the intake to see if it was TOO open, ie no filter, just bogged as normal.

Now you have me scratching my head a bit...it had a bottom main jet as I remember. A bottom main that the needle seated into with a little plastic splash guard disc thingy.

 

[WRW9751]

There is a mechanical advance in those, behind the mag. It's probably not advancing. Just needs cleaned up also. You can look into the slot on the mag and see a steel lever. Try to move it, its spring loaded. You might be able to dislodge it without removing the flywheel. A simple screw in Yamaha flywheel puller is all you need. They are all over the web. $15/20.

 

[wfopete]

On a 2 smoker that old also check the exhaust for carbon, mouse nest and dirt dabbers.

Those guys really kill the top end power.