Brakes Right way to slow down and brake with these HT engines?

RuiGomes

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My bike is now ready and I went for a small ride around the block. However, I didn't manage to properly slow down and brake.

I lightly pressed the brakes and released the throttle. Then I pressed the clutch lever, but as soon as I did that the motor sounded like it was going to explode (like 12k RPM) and everything was vibrating much more than when riding normally on the motor, I was afraid to damage something.

How do you guys brake on these things?
 
release the throttle, pull in the clutch and apply the brakes.
if your engine revved out of control when you pulled in the clutch, it sounds like your throttle is stuck or you have a massive air leak.
make sure that you have the slide inserted in the carb correctly. It can go in 2 different ways but only one way is correct.
the slide, which slides down into the top of carb. You have to unscrew the top cap on the carb and lift to get the slide out.
the slide has 2 slots in the sides, a long slot and a short slot.
Make sure that the long slot is on the right side (when looking down at the top of the carb). The long slot lines up with a pin that's cast into the inside of the carb. The short slot goes to the left and lines up with the idle screw.
if you have the slide in backwards, your throttle will stick wide open.

It's also possible that your throttle cable is binding up and causing the throttle to stay wide open, or the slide is binding up in the carb.
when you release the throttle and pull in the clutch, your engine rpms should drop to an idle, it should not rev up.
 
Sounds like your throttle cable is sticking; the engine trying to run at full throttle or your carburettor slide is sticking at wide open throttle.

Either way, if you've pulled in the clutch, your engine has revved out of control. The big end connecting rod bearing is now totally f*&ked.
Just a matter of time before the needle rollers in the big end eject themselves from the connecting rod and fly all around the bottom end before getting stuck in between the piston and cylinder wall; locking up the engine.
Best case scenario is that the needle rollers fly up through the transfer ports and hammer the top of the piston and the cylinder head.

At this point, it's best to purchase a new crankshaft and connecting rod assembly and rebuild the engine.
 
The throttle cable is installed the right way (biggest hole to the right side of the carb) and I am able to use it properly when riding (if I push the throttle it accelerates as it should).

@Fabian, it that would happen, was it supposed for the motor to work properly when I'm not using the clutch? I'm able to start it and be pushed on idle and I can even give it more throttle and it accelerates very well.
 
I doubt that the motor is trashed.
I think that your throttle is sticking. sometimes if you over tighten the carb cap, it can distort the carb body, making the slide get stuck.
ride it & when it does it again, hit the kill switch to kill the motor but don't touch the throttle.
let the engine shut off, remove the air cleaner & look into the carb to see if the slide is stuck. it is also possible that your cable is too tight which will cause it to bind & make the throttle stick open.
do you have wire ties holding the cable to the frame? If so, the can make the cable stick inside the cable housing if they are too tight.
also, the twist throttle may be sticking.
put some oil down into the throttle cable and grease up the twist throttle.
if you have an air leak, it will rev out of control all the time.

post a pic. of your carb & throttle assembly. also show the cable routing.
 
I doubt that the motor is trashed.
I think that your throttle is sticking. sometimes if you over tighten the carb cap, it can distort the carb body, making the slide get stuck.
ride it & when it does it again, hit the kill switch to kill the motor but don't touch the throttle.
let the engine shut off, remove the air cleaner & look into the carb to see if the slide is stuck. it is also possible that your cable is too tight which will cause it to bind & make the throttle stick open.
do you have wire ties holding the cable to the frame? If so, the can make the cable stick inside the cable housing if they are too tight.
also, the twist throttle may be sticking.
put some oil down into the throttle cable and grease up the twist throttle.
if you have an air leak, it will rev out of control all the time.

post a pic. of your carb & throttle assembly. also show the cable routing.
That is great advice. I remember my first build, the throttle was a Murphy's Law kinda thing. Cable binding, over-tightened the cap, etc. One thing you missed was to make sure the carb throat is butted up against the intake, mine felt like it did, but had a small burr keeping it from sliding all the way in, creating a massive air leak which caused high rpm idle.
 
The motor may not be trashed "right now" but the damage is done. Those big end connecting rod needle roller bearings have all got flat spots on them.

From this point onwards, it's just a matter of time before the case hardening breaks up and exposes the soft base material - i wouldn't give it more than 500 kilometers before the big end bearing fails, either locking up the motor, or spitting the needle rollers out the exhaust and bead blasting the cylinder head and piston face.

After such high revs, the motor is effectively trashed...
 
okay another thing to try is adjust the set nut and screws on each end of the throttle cable.You might have them set to tight.If needed you also can take the set screw nuts off for more adjustment.That should drop the carb slide down farther in the cylinder for normal idle.
 
If engine speeds up or won't drop down to idle right away, it means you are lean and probably have an airleak. as for braking, I just pull the brake handles until I come to a stop. My HT engines all have a centrifugal clutch and I don't have to worry about that nonsense.
 
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That is great advice. I remember my first build, the throttle was a Murphy's Law kinda thing. Cable binding, over-tightened the cap, etc. One thing you missed was to make sure the carb throat is butted up against the intake, mine felt like it did, but had a small burr keeping it from sliding all the way in, creating a massive air leak which caused high rpm idle.
possible, but if it had a massive air leak, it would rev high out of control all the time. he says that it idle fine & only revs high while riding it & pulling in the clutch when coming to a stop.
he said it isles fine until he tries to ride it.
 
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