1981 Yz465 Performance (none)

A

ALOHA

Member
Sep 29, 2009
14
0
I am having a real tough time getting my 1981 yz465 to run properly.

Problems I have experienced:
1. Very hard to start. Kick, kick and kick some more before it starts.

2. Will not run above 3000 to 3500 rpm. from 1/2 throttle to full throttle it just blubbers. It will not clean out.

What I have done:

1st over bore, new piston and rings. (piston is in correct)
New seals, complete motor.
gone through the carb 4 or 5 times. Now has all stock jetting. 45 pilot, 390 main, new needle and needle jet.
reset the float a little lower from the 1.1 height called out
replaced the coil under the tank.
replaced the stator on the crank.

No change. It still will not pull after the 1st 1/3 of throttle and just blubbers. Still will not clean out regardless of how long I keep the throttle on.

Any ideas. It's driving me nuts

Thanks
Jack
 
A

AjayMike

Mi. Trail Riders
Member
Mar 9, 2003
49
0
You may have a plugged exhaust system. Is the silencer plugged up? Very common on older scoots. If it's a clamp-on silencer the solution is simple: Remove it and test to see if the problem disappears. If the expansion chamber has a built-in silencer system, it's not quite so simple. It's tough to get them apart sometimes and figure out what's plugged. Back in the Old Days when two stroke street bikes were common, if we suspected a plugged muffler we used to remove the entire pipe and give the bike a quick run through the gears to see if the problem went away. A brief run without a pipe won't hurt it, although it sounds ungodly. It probably won't run very well without a pipe, but it should start and rev up OK. Worth a try, after all the work you've done.
Mike
 
whenfoxforks-ruled

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
Covered everything but the first thing you should have changed, the float valve and seat if applicable. It sure sounds like its flooding/rich? If that does not do it, perform a leak down test on your motor.
 
Rooster

Rooster

Today's Tom Sawyer
Damn Yankees
LIFETIME SPONSOR
Aug 24, 2000
3,292
1
I'm waiting for Super Hunky to jump in on this one :p
 
J

JohnRichardson

Member
Oct 4, 2009
5
0
YZ465 not revving out

A YZ was not designed to run with an after market slip on silencer but should still accept one with no trouble. Check the air filter isn't too oily and the best way of cleaning an expansion chamber or any 2stroke exhaust is to burn it out from the inside using a hot gas flame (it may ruin chrome on road bikes system) We used to use oxy/acetyline with compressed air line blowing in to keep the carbon deposit burning. You can get the whole pipe glowing red if you so desire but not advised. Re paint with a heat resistant spray can flat black or what have you. The problem is most certainly induction and either not enough air or too much fuel. When the motor was rebuilt were the crankshaft o'rings renewed as well as the seals?
 
H

helio lucas

~SPONSOR~
Jun 20, 2007
1,020
0
stupid question but, spark plug ok?
 
A

ALOHA

Member
Sep 29, 2009
14
0
Yz465 Not Running Good

I am expecting to recieve a new needle and seat today and install it tonight. The spark plug is new. I have repacked my silencer as well. After I go through the carb install the new needle and seat, re-set the float height. I will re-seal the exhaust at the header slip joint with high temp silicone.

At that point I should be ready to give it a try again. It will have to be Tues afternoon as it will be to late tonight to fire it up.

Thanks
Jack
 
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