Clone is hunting at high rpm

[blkscorpion80]

Guys I have a 6.5 on my trailhorse and its running like :001_9898:. Before I had the clone on the TH, I had it on my arco (straight drive) and I had the same issues but on a smaller scale. I could actually get it to full throttle before it would act up. Basically when I try to wind it out, the gov. kicks in way to early and the engines starts to hunt. It maybe reaches 3/4 speed and drops rpms really quick and then kicks back up to the 3/4 speed it was recently at. The engine will not hold a steady rpm regardless of how fast the bike is ging. Also when I let off of the gas it backfires big time. The first time I heard it back fire, I thought somebody finally got tired of me riding through the neighborhood at night :biggrin:. I also tried running the engine with the choke in different positions-no luck

Trail horse:

Clutch- 12t
Jackshaft- 13t AND 18t
Drive wheel- 60t
6" wheels

 

[isaacson06]

Well my gearing on nine is clutch 12 jackshaft18 other jackshaft 13 and and rear wheel is 32 and it should do 43mph at 4500rpms and tours will only do 3600rpms with the gov. maybe your gearing is really short and its reaching fuLl speed really fast. I also have 6" wheels
Ill check the speed for sure when I get home cuz I'm at work on my phone so I can't do much

 

[blkscorpion80]

It does get to 3/4 speed really fast almost instantly. What effect does this have on the engine not maintaining a constant rpm?

 

[The Restore Kid]

It sounds like if it is reving up real good but then cutting back, then jumping up again.. Probably your carburetor is trying to run about right, but the spring tension in your governor system is not right. Like the spring is too tight probably.. The engine gets to speed then the the governor snaps it back shut, realizes it's not going fast enough, then lets tension back off the spring and it can go again....

If you look at the governor setup there should be different holes along where the spring attaches that will let ya move it up or down the arm to gain or lose leverage and spring tension.. Try moving the spring farther down the arm closer to where it rotates from... That should allow you to pull it open farther and give the spring less leverage and less ability to jerk back on the governor so hard...

 

[isaacson06]

Cuz its reving so fast and hits the gov and the gov tries to kick it back down and u just keep trying to go.

 

[blkscorpion80]

I'll try moving the spring when I get home. Hope this works. Man was she climbing some reaaally steep hills last night with the jackshaft setup.

 

[supernova]

I'll try moving the spring when I get home. Hope this works. Man was she climbing some reaaally steep hills last night with the jackshaft setup.

If I back the throttle stop screw out too far mine will act up, I am greedy and want more than it is willing to give me at WOT. The spring is an issue and when I relocated it to the farthest hole it gave me less trouble and I found the sweet spot on the stop screw! Both my cloned DBs had this issue and I think it is pretty common, you'll find a happy medium with some adjustment. Good luck!:thumbsup:

 

[blkscorpion80]

I never had this problem until I just bought the last two clones in march. The other clones had zero problems and ran as I thought they should. I guess I keep trying to compare these these to the old ones. I hope it gets worked out. I also have a tec H50 that is not running right. For some reason I can get the gov. adjusted back to specs. I think I'm going to just pull the Gov. this weekend and be done with it. Either way I have to hurry and get these two bikes out of the way. The time has come to get the Sea Doos back on the water.

 

[blkscorpion80]

Can someone help me find the post that explains how to get a little more rpms out of the gov. by ziptieing the spring.

 

[novaracer]

remove the gov with stock valve springs it wont rev to high.

 

[blkscorpion80]

Ok now this is starting to get embarassing. My son is blowing by me on a stock db. The 6.5 pulls like a monster until it reaches 20mph. After that It starts acting up. I have moved the spring to the lowest possible slot on the arm, and it has improverd a little,but not much. This is starting to tick me off.

 

[supernova]

Ok now this is starting to get embarassing. My son is blowing by me on a stock db. The 6.5 pulls like a monster until it reaches 20mph. After that It starts acting up. I have moved the spring to the lowest possible slot on the arm, and it has improverd a little,but not much. This is starting to tick me off.

Remove the governer, I am doing it on my blue DB! I have heard argunents both ways and if you're not happy just do it! If you dont run the thing full out for a long distance it is doubtfull it will grenade, you just wont see that many RPMs! You are an adult and I'm sure you are smart enough to know when you are near the danger zone, just like shifting a motorcycle you know when to shift by the sound and know if you push it it is toast! The same applies to the DB you'll know when you're there! Good luck!
Disclaimer: supernova accepts no blame or liability for you in the event you take my advice and die or are maimed by the DB grenading!

 

[minibikedude]

I having the same issue on my Murray bike. Yesterday, I made the shorter linkage like it show on affordable go cart site. Simple fix. No governor anymore. Stock throttle set up. My motor stock except the header. I just watch topping out the motor, much smoother riding down the road with out it.
Also what supernova said, Rider takes all responsibility.

 

[blkscorpion80]

Guys I'm not trying to be ignorant about the whole thing. It frustrates me because I have several clones that I did not remove the gov. from and they had enough top end for the setup that I had. This motor will only give me half of the topend speed as my other clones gave me. If it would run correctly I wouldn't need to remove the gov. Hey minibike dude lets see that murray.

 

[supernova]

Guys I'm not trying to be ignorant about the whole thing. It frustrates me because I have several clones that I did not remove the gov. from and they had enough top end for the setup that I had. This motor will only give me half of the topend speed as my other clones gave me. If it would run correctly I wouldn't need to remove the gov. Hey minibike dude lets see that murray.

This latest batch has done this, both my current clones do it! The first one I ever had was not a greyhound and did not, it just said lifan and I bought it second hand NIB from a dude who's kid raced carts, he said they allowed better Box Stock engines and he never opened it. I paid $100 and put it on an old DB with the chrome tip grips and it ran like a banshee! No surging and plenty of speed, even more when the throttle stop screw was backed out! I sold it and the dude still has it, but wont sell! I am leaving one in the sweet spot as far as the throttle stop screw with decent top speed before surging so my son can ride it! The Blue DB will be getting the Gov. removed as I am the only one who rides it!

 

[Oldschool]

There is one more adjustment.
The arm to the governer shaft. the angle this was set at the factory could be off.

What your discribing sounds like the governer is running in an unstable area.

Have you ever heard motor boat noises coming from a guitar Amp? Or seen a generator that reved up and slowed down at certan speeds but otherwise worked fine at other loads?
These are all caused by the same thing a closed loop feedback control system running in an unstable area trying to and over/under correcting for the area of opperation.

Its a bugger to fix in a mechanical system and an equal pain in the arse in electronics or instrumentaion. There are mathimatical ways to graph and plot the zones of instability and fixes to provide stable opperation.
But in your case I would Take a good hard look at the linkages and springs something sounds like its out of whack.
The Good news is if you completely remove the governer and keep the engine stock your probably not going to have anything to worry about and odds are you can do a better job of regulating the speed by ear lol....

Just don't soup it up without some billet parts for safety and invest in a cheap tack to be sure your staying under 5000 rpm.

 

[minibikedude]

I not sure if my new clone engine has something installed wrong or adjusted wrong, I was not sure on the way to set them up on the clone engine I do not have a service manual. Mine would pull like crazy and I think it was running above the 3600 Rpm and then it would slam shut like you let off the throttle and then snap wide open again. So I by passed it, The governor still in the engine. I will remove it someday when I get a rod and flywheel. I do not think being box stock it going to blow up. I can tell the valves are floating once up to full speed under a short full throttle run. I do not like governed engine that well. It just runs a lot smoother with out that governor in it.
I have more pictures under a thread. My Murray bike

 

[Oldschool]

By bypassing it without removing all the parts you can be fairly sure washers and pieces are loose in the bottom crank case now...

 

[minibikedude]

Its fine, Nothing is left apart to come apart, the governor arm still in tack on the engine. I ran about 10 miles on it already with no problems.

 

[The Restore Kid]

If the (the latest ship load) comment is correct..... It very well may be the springs in this batch of motors is too stiff.. You could also try getting another spring from the hardware store with a lighter pull... Chinese sweatshops don't have the highest Quality Control standards..