No power on new motor

[Wolfshoes]

A key clue to the low power could be the four stroking observation since from my experience, this issue has been related to the stock spark plug performance. Perhaps the timing is late and compression is beyond peak to the point it is not firing properly at the higher rpm's; also explaining the smoke. Since this is not normally adjustable, that would make it a factory issue. A comparison of magnet positioning at top dead center with the old motor may provide a clue. Timing could be adjusted by using magnets from other sources which may be notched for the key slot differently or better yet, with Jaguar's adjustable CDI. Sending the motor back would also not be out of range of being reasonable if it clearly is defective.

I have been attempting to break in a replacement engine with low power but the symptoms are different than yours.

 

[Tyler6357]

Are you certain there are no air leaks, especially around the head? Sometimes small air leaks can make it idle okay but once the load is on it leaks. Try revving the engine without a load and see if you can feel any air shooting out around the head/head gasket. I bet China makes 1000s of warped stock heads right out of the factory. A good test might be to just try it with your old head. Also, if it's smoking extra, you might be using too much oil in your mix or you might just be running really rich, keep the clip on the leanest setting and/or get a smaller jet. It's not unusual for the exact same engine to need different sized jets, I have an engine that loves a #60 and a second exact same engine that likes a #65.

 

[inspectorcritic]

So I accidentally destroyed my last motor and ended up getting a new one a couple days ago. I ended up exchanging just the motor and used pretty much all of the old components. The old motor was working fantastic before I broke it (stripped head stud holes, then stripped the helicoils). After getting everything assembled, the new motor was running piss poor. It will idle, but once the clutch is engaged it has very little power (cant go up any inclines without having to pedal assist, top speed on flat ground at WOT only around 15-20mph.) It seems to be fourstroking, but I'm not entirely positive on that.

I first thought it was something electrical that was the problem as I got sloppy with the wiring. I then replaced the kill switch, magneto, and CDI. Problem persisted.

I then replaced the spark plug with a b6hs and the problem still persisted.

I then took the air filter off the carb to see if it was restricting the airflow. Still had the problem without the filter.

I then swapped the carb out for a different one. Still had the problem.

Adjusting c-clip also seemed to do nothing.


The exhaust is super smokey and the plug looked wet with oil after all this testing so I assume it must be running way too rich. I just don't understand why, as both of my carbs worked great on the old motor with the same jets.

I don't see any sort of gasket leaks, but my second guess is a loss of compression due to the problem being only while the motor is under load.


Next I guess I will swap out the muffler in case it's clogged, but the muffler I'm using had less than 100 miles on it running 1:32 full synthetic, so I doubt it's clogged.

The only other thing I can think to do is just port and polish it and trim the piston skirt to get better flow, but I doubt it will help.

Any ideas or suggestions? I'm more or less at a loss

Some are junk out of the box had em before look at your warranty.

 

[Guest-808796]

How much compression has it got?

 

[Wrench]

Guest-808796
I guess you just wanna check after a couple of years

 

[inspectorcritic]

So I accidentally destroyed my last motor and ended up getting a new one a couple days ago. I ended up exchanging just the motor and used pretty much all of the old components. The old motor was working fantastic before I broke it (stripped head stud holes, then stripped the helicoils). After getting everything assembled, the new motor was running piss poor. It will idle, but once the clutch is engaged it has very little power (cant go up any inclines without having to pedal assist, top speed on flat ground at WOT only around 15-20mph.) It seems to be fourstroking, but I'm not entirely positive on that.

I first thought it was something electrical that was the problem as I got sloppy with the wiring. I then replaced the kill switch, magneto, and CDI. Problem persisted.

I then replaced the spark plug with a b6hs and the problem still persisted.

I then took the air filter off the carb to see if it was restricting the airflow. Still had the problem without the filter.

I then swapped the carb out for a different one. Still had the problem.

Adjusting c-clip also seemed to do nothing.


The exhaust is super smokey and the plug looked wet with oil after all this testing so I assume it must be running way too rich. I just don't understand why, as both of my carbs worked great on the old motor with the same jets.

I don't see any sort of gasket leaks, but my second guess is a loss of compression due to the problem being only while the motor is under load.


Next I guess I will swap out the muffler in case it's clogged, but the muffler I'm using had less than 100 miles on it running 1:32 full synthetic, so I doubt it's clogged.

The only other thing I can think to do is just port and polish it and trim the piston skirt to get better flow, but I doubt it will help.

Any ideas or suggestions? I'm more or less at a loss

Take the battle out of the exhaust there is a 10mm nut on a screw take it off tap on the end with a wrench it will fall off and give you 15 - 20% more power except it's noisey as hell!

 

[FurryOnTheInside]

Compresion:
Since 2018 when this thread was posted, I have changed the way I talk about compression. I'm still not actually saying it right and having to return to edit my posts.
I should really only refer to the measurable value as cranking pressure, and the calculated value as compression ratio, since we can only ever infer things about compression of a running engine (from our measurement of cranking pressure and our other knowledge of the specific engine) on an engine that has the compression gauge screwed into the spark plug hole, and therefore is a non-running engine at the time, turning at an extremely low rpm, and with no tuned pipe effect.

We never get to measure and know the actual compression psi in the combustion chamber, in use.
This is even more difficult when we start using a proper 2-stroke exhaust system that is tuned to resonate and cause pressure waves that improve our scavenging and increase compression at specific RPM range.

It is still good to measure everything we can measure. Any data we can add to what data we have is surely valuable, if interpreted and used correctly.
Finer and finer measurement; coupled with better, truer interpretation of the data collected is the basis of human scientific progress since the beginning!


That said, now I think this may have had nothing whatever to do with low compression, and everything to do with a broken Woodruff key.

OP said there was clicking and power loss under load. I think I would have to take a little look under the output sprocket, the output gear, then the cluch hub.. looking for a broken key and some scraped and worn shaft. Just a hunch, but totally cost-free to check this and you don't even need any measuring tools. The keys are intended to break and be replaceable. We should all have a pack of spares (cost $2).

Btw you still need basic measuring tools for the hobby or anything technical that you will have to deal with in adult life. If parents don't buy their kids digital calipers at the very least that's neglect imo and forces them, from the start, to rely on paying others for things that shouldn't even cost us anything.
Like, kids need to be taught how to drive, by their parents, for free, or it might never happen, and that would make them disadvantaged for their whole life.
(....Grumble grumble. Moan, moan. I'm old and bitter and I need a toilet frame or I get trapped there and have to call the nurse....) ☺

 

[inspectorcritic]

Did you take the guts out of your exhaust like I said?
I had a bad Moto from gaz bike that was the only I could get it to climb a hill try see if it works for you and let me know about the test please.

 

[Wrench]

Did you take the guts out of your exhaust like I said?
I had a bad Moto from gaz bike that was the only I could get it to climb a hill try see if it works for you and let me know about the test please.

Inspector, You realize @James Owens Thread is from 2018 and he ain't been seen since April 2018

 

[Rodhead]

So I accidentally destroyed my last motor and ended up getting a new one a couple days ago. I ended up exchanging just the motor and used pretty much all of the old components. The old motor was working fantastic before I broke it (stripped head stud holes, then stripped the helicoils). After getting everything assembled, the new motor was running piss poor. It will idle, but once the clutch is engaged it has very little power (cant go up any inclines without having to pedal assist, top speed on flat ground at WOT only around 15-20mph.) It seems to be fourstroking, but I'm not entirely positive on that.

I first thought it was something electrical that was the problem as I got sloppy with the wiring. I then replaced the kill switch, magneto, and CDI. Problem persisted.

I then replaced the spark plug with a b6hs and the problem still persisted.

I then took the air filter off the carb to see if it was restricting the airflow. Still had the problem without the filter.

I then swapped the carb out for a different one. Still had the problem.

Adjusting c-clip also seemed to do nothing.


The exhaust is super smokey and the plug looked wet with oil after all this testing so I assume it must be running way too rich. I just don't understand why, as both of my carbs worked great on the old motor with the same jets.

I don't see any sort of gasket leaks, but my second guess is a loss of compression due to the problem being only while the motor is under load.


Next I guess I will swap out the muffler in case it's clogged, but the muffler I'm using had less than 100 miles on it running 1:32 full synthetic, so I doubt it's clogged.

The only other thing I can think to do is just port and polish it and trim the piston skirt to get better flow, but I doubt it will help.

Any ideas or suggestions? I'm more or less at a loss

Check seals lap head and cylinder for true flatness just enof to get good seal. Crank seals leaks will cause very poor performance. Set plug at 24. Check for leaks. Set float. Clean and check carb. Check for blue spark.fresh gas. Check jetting. Hope this helps