yz400

[anthony28]

my dad got a 1977 yz400 a week ago and we cleaned the carb and the bike wont kick start. but we start it by putting gas were the spark plug goes the it kicks but thats how we have to start it every time and he doesnet want to go far with the bike incase it dies then we can start it so.. plz help ty

 

[VintageYZ1981]

my dad got a 1977 yz400 a week ago and we cleaned the carb and the bike wont kick start. but we start it by putting gas were the spark plug goes the it kicks but thats how we have to start it every time and he doesnet want to go far with the bike incase it dies then we can start it so.. plz help ty

The fact that the bike starts after you put gas in the plug hole indicates that it's not getting enough fuel. Go back to the carb and clean it again, soak it in kerosene or carb cleaner overnight, disassemble and clean again thoroughly. Also check the petcock and fuel tank and make sure there is no blockage.
Good luck.

 

[anthony28]

ty ill try that

 

[kingbrian]

have you adjusted the idle once its running?

 

[anthony28]

have you adjusted the idle once its running?

yes but it does not make it start better

 

[magneto]

My procedure on my CR500 is to lay it on its side for a few seconds to get some gas into the motor, choke it if it is cold, kick it over slowly a few times and then find the start of the compression stroke. Take up the slack on the kickstart and then give it a healthy kick. If the bike is warm it is not usually necessary to choke or lay the bike on its side.

Check your float level.

 

[anthony28]

My procedure on my CR500 is to lay it on its side for a few seconds to get some gas into the motor, choke it if it is cold, kick it over slowly a few times and then find the start of the compression stroke. Take up the slack on the kickstart and then give it a healthy kick. If the bike is warm it is not usually necessary to choke or lay the bike on its side.

Check your float level.

thx ill try tht

 

[anthony28]

help

srry guys but none of ur tips did nethin but thx for trying

 

[j32]

clean and oil the air filter
?? hows the stater crank seal? is it leaking
i had a it400 bored to the max, new seals,jetted ,and didn't have any problems
it would have been a great cart motor lol
i used a -ngk b8es spark plug
-check the reeds ,get some boeysen reeds,does it have good compression?
might be time for new rings?
try klotz oil for the premix
change the silencer packing

try these things before jumping into jetting
that it i had was amazing lol,after a little work
it is ?29 years old
good luck

 

[Sawblade]

I would clean out the carb again and also replace the jets with new ones. A rebuild kit is what fixed my problem earlier this year on a TAM 75.

 

[magneto]

Does that bike have points or electronic ignition? Check your point gap if it has them. Check your timing in either case.

 

[Britt Boyette]

It's a CDI.
Try a new carb . Sometimes, it's not worth the hassle to goof around with a worn out carb. When you do this, replace the fuel line and use quaility gas/ premix at 40:1 and see the jetting tips guide over at the 2 stroke area.

 

[anthony28]

thx guys ill try ur new tips thx

 

[j32]

dont use 40:1 on a air cooled bike-its probbably too lean-try 32:1
you might need a new crank seal? whats it run like when you do get it running??
or new reeds

 

[Husky Texan]

Replace the pilot jet in the carb for sure. You may think it's clean, but your symptoms say it isn't. Spend the 5 bucks and be happy.

 

[kingbrian]

40:1 should be fine i ran nothin but duralube and golden spectro at 50:1 in all of my pre 80 bikes my 75 sc5oo loved it the most. but i had an 79 yz125 that i thought ran great except it wouldnt idle (push started it) then i replaced the piston and ring because they were now one peice then the bike was completely different then it ran great. might be worth the inspection.

 

[anthony28]

if your crankseals are gone is it harder to start.

 

[j32]

i didnt say it wouldnt run on 40-or 50:1
just that its air cooled and needs more lubrication they get hot!!!

 

[Britt Boyette]

Trust me, 40:1 with synthetic works fine. I do have a small bit of time on these kind of bikes and there are no problems with 40:1.

 

[anthony28]

thx guys but nothing helped its still rthe saMe

 

[originaldirt]

Now to diagnose the real problem.
(1)Remove the left hand engine case cover that covers the mag/dyno.( Usually 4 screws)
(2)Grab the flywheel and attempt to move it up/down, left right, in/out. Anyway but
circular in direction.
(3)If you detect any clicking or motion other than circular, you need new crank bearings
and seals for a minimum. A major rebuild $$$$$$$.
(4)Inspect the area around the flywheel, inside the cover, around the statot plate for
any signs of moisture/wetness. If it is oily, smells like gas, or has what appears to
be sweat drops in that area, the crank seals are shot for sure....se item #3.
*****
Two strokes are basically air pumps that pull in air/fuel on the up-stroke from the carb/inlet to the lower end area of the engine. Then once the mixture from the previous rotation fires above the piston, the downward force of the piston pushes (scavenges) the fuel/air in the lower end thru the transfer ports and reaches the top end just as the piston starts upwards again. So, with bad crank bearings and seals you get no lower end "pressure" at all when the motor is not tuning over continuously, but fuel fed directly to the top end via drops in the plug hole will provide enough fule to make it start. Once running there is residual, but declining lower end pressure developing enough pressure/vacuum to keep it running for a while. Once the seals andbearings are really toast. the motor will develop an air leak and run wide open until it grenades itself. Be forewarned.!!

OriginalDirt

 

[COMBEN]

don't touch throttle when starting?

Hi,

All of the previous suggestions are very sound and great advice, but before you start pulling her apart try this............ you never know :whoa: ....I'm assuming you have new fuel in the tank and carb ;)

....fuel on, choke on and then just try kicking her over but don't touch the throttle at all, right hand in your pocket.

Some bikes are a real bugger to start when cold if you give them a sniff of throttle (causes a loss of vacuum for the choke circuit)....my now sold '03 KDX-220R was the best example of this, nothing wrong with it it's just how they are, she started 1st/2nd kick with no throttle, but give her some gas and you could kick all day long :bang:


....ohh and when hot started 1st lick with 1/4 throttle

good luck

 

[anthony28]

ok thanks ill try these o and ill try to get a pic of it.

 

[anthony28]

Now to diagnose the real problem.
(1)Remove the left hand engine case cover that covers the mag/dyno.( Usually 4 screws)
(2)Grab the flywheel and attempt to move it up/down, left right, in/out. Anyway but
circular in direction.
(3)If you detect any clicking or motion other than circular, you need new crank bearings
and seals for a minimum. A major rebuild $$$$$$$.
(4)Inspect the area around the flywheel, inside the cover, around the statot plate for
any signs of moisture/wetness. If it is oily, smells like gas, or has what appears to
be sweat drops in that area, the crank seals are shot for sure....se item #3.
*****
Two strokes are basically air pumps that pull in air/fuel on the up-stroke from the carb/inlet to the lower end area of the engine. Then once the mixture from the previous rotation fires above the piston, the downward force of the piston pushes (scavenges) the fuel/air in the lower end thru the transfer ports and reaches the top end just as the piston starts upwards again. So, with bad crank bearings and seals you get no lower end "pressure" at all when the motor is not tuning over continuously, but fuel fed directly to the top end via drops in the plug hole will provide enough fule to make it start. Once running there is residual, but declining lower end pressure developing enough pressure/vacuum to keep it running for a while. Once the seals andbearings are really toast. the motor will develop an air leak and run wide open until it grenades itself. Be forewarned.!!

OriginalDirt

the fly wheel was stable and everthing else ur said is working

 

[dirtdealer726]

Pull start the bike and then ride it around some. Many bikes just need some riding time in order to clean out and run properly. When kicking it over, make sure you kick it from the top dead center. If you don't let the kickstarter come back far enough, then you can't get a good enough kick.