How long can "China doll" hold at WOT? Also, high altitude (+gear reductions and "too lean?")

[DAMIEN1307]

How about engine breaking?

Your gonna hear people on both sides of this issue...lol...I do "engine braking" but it is never more than really a few seconds worth along with the brakes and then pull in the clutch to stop at signs, lights, etc....I just avoid extremes with anything...In moderation, I find nothing wrong with it.

 

[DAMIEN1307]

Also, be sure to check the four head bolts on top of motor after each ride during the break-in period and then periodically thereafter because as it heats up and cools down during heat cycles, they will loosen up and need to be retorqued to 12 ft pds, (144 inch pds), to avoid head gasket leaks and lousy performance etc. etc...DO NOT OVER TIGHTEN !!!

Ps...NEVER retorque when still hot...It has to be completely cold to do this properly.

With these chinesium aluminum heads, It's not so much that the nut's are coming loose, but the aluminum threads are shrinking and expanding under the torqued down nuts during heat cycles.
As the aluminum shrinks and expands under the nut's, washers, and lock washers, it makes it appear like it's the nuts backing off and loosening up,
So re-torqueing is quite necessary.

 

[Kehkou]

Your gonna hear people on both sides of this issue...lol...I do "engine braking" but it is never more than really a few seconds worth along with the brakes and then pull in the clutch to stop at signs, lights, etc....I just avoid extremes with anything...In moderation, I find nothing wrong with it.

Yes, moderation is key (esp. for a moderator). There are too many crazies with pit bikes and such out here. Tragic stuff.

Also, be sure to check the four head bolts on top of motor after each ride during the break-in period and then periodically thereafter because as it heats up and cools down during heat cycles, they will loosen up and need to be retorqued to 12 ft pds, (144 inch pds), to avoid head gasket leaks and lousy performance etc. etc...DO NOT OVER TIGHTEN !!!

Ps...NEVER retorque when still hot...It has to be completely cold to do this properly.

With these chinesium aluminum heads, It's not so much that the nut's are coming loose, but the aluminum is shrinking under the torqued down nuts.
As the aluminum shrinks under the nut's, washers, and lock washers, it makes it appear like it's the nuts backing off and loosening up,
So a few re torques are needed.

^Listen to this advice!

I keep a torque wrench by my bike and check the head nut torque before each ride, along with the chain, clutch, brakes, fuel, etc. while the cylinder 'tempers' during break-in. I use 8 ft/lbs (96 in/lbs); 12 stripped the case on my original engine. I think the 12-year-old Chinese boy who assembled it must have cross threaded the bolts.

 

[Sidewinder Jerry]

In the past many argued how good they were by controlling their rpm level by ear and that a tach wasn't needed. It seems years of preaching has reached several and they see the true value of using a tachometer. The good news is the tachs are very affordable and can be purchased from eBay or Amazon.

 

[DAMIEN1307]

The good news is the tachs are very affordable and can be purchased from eBay or Amazon.

Perhaps you might have a URL link to a decent one at Amazon???

 

[Sidewinder Jerry]

Perhaps you might have a URL link to a decent one at Amazon???

Small Engine Tachometer Hour Meter: Timorn Digital Inductive Waterproof Tiny Tach Meter & RPM Meter & HR Meter for Dirt Bike | Chainsaw | Lawn Mower | Generator Motorcycle Boat Marine Outboard https://a.co/d/21ICatm

 

[Kehkou]

Small Engine Tachometer Hour Meter: Timorn Digital Inductive Waterproof Tiny Tach Meter & RPM Meter & HR Meter for Dirt Bike | Chainsaw | Lawn Mower | Generator Motorcycle Boat Marine Outboard https://a.co/d/21ICatm

I was thinking of getting this very one (it could have been a clone). I like how it has a service reminder. I'm curious how fast it refreshes the reading.
Edit: It says in the description "0.5s or 1s".

With these chinesium aluminum heads, It's not so much that the nut's are coming loose, but the aluminum is shrinking under the torqued down nuts.
As the aluminum shrinks under the nut's, washers, and lock washers, it makes it appear like it's the nuts backing off and loosening up,
So re-torqueing is quite necessary.

I use 8 ft/lbs (96 in/lbs).

Interesting observation: my head nuts haven't been "backing off" at 8 so I increased torque to 10, but the nuts still click the wrench without budging. Could it be that my "improved engine" also uses a better grade chinesium? 10 ft/lbs is within spec.

 

[Sidewinder Jerry]

I was thinking of getting this very one (it could have been a clone). I like how it has a service reminder. I'm curious how fast it refreshes the reading.
Edit: It says in the description "0.5s or 1s".



Interesting observation: my head nuts haven't been "backing off" at 8 so I increased torque to 10, but the nuts still click the wrench without budging. Could it be that my "improved engine" also uses a better grade chinesium? 10 ft/lbs is within spec.

The other good thing about a tachometer is it can be used to fine tune the carburetor. The hour counters are very nice for maintaining a maintenance schedule

 

[Kehkou]

The other good thing about a tachometer is it can be used to fine tune the carburetor.

What do you watch for on the tach while tuning, and how do you translate it to the adjustments?

 

[ImpulseRocket]

Interesting observation: my head nuts haven't been "backing off" at 8 so I increased torque to 10, but the nuts still click the wrench without budging. Could it be that my "improved engine" also uses a better grade chinesium? 10 ft/lbs is within spec.

There are a lot of factors at work in regards to fasteners backing off. There is more to it than simply thermal expansion/retraction. Engine vibration is another part of that, and even the primary frequency of that vibration in relation to the materials, size of the fasteners, etc. If you have an engine with a balanced crank the lower vibrations can lead to less issues with hardware coming loose.

I am a practitioner of "Overkill" when it comes to fastener retention. After 3 heat cycles on my own Phantom 85, the nuts also stopped backing off. This was with me actually torquing them tighter than 12lb-ft because an M8 stud and nut can handle close to 30, and the case side has more than sufficient thread engagement on the stud, even with cheap/crappy alloy used to cast the cases. I just made sure to do it in stages of 5 ft-lbs to be safe, and eventually tightened them to 15lb-ft/180in-lb, all in a criss cross pattern.

The hardware in question was not the stuff that the engine came with either, but grade 10.9 metric hardware I purchased myself, including the studs.

The overkill part though, isn't any of the above really, but the fact that my head is retained by a washer, lock washer, a nut, and then a jam nut. Both of which have Loctite 243 applied. I am not a fan of hardware coming loose.

As a side note, a fun trick you can use to track your hardware is to use a marker or grease pen and put marks on the nuts and head that align after tightening them. This gives you a visual point of reference to track if the nut has moved at all.