So, I installed this new kit on my new bike and it's been running well and very healthily with little vibration and nothing needing to be replaced so far. However, I've noticed that over time as the engine heats up it sort of starts to lose power until I end up with around half the power I had when I started it ten-fifteen minutes ago. What gives?
Losing power after warming up?
- Thread starter fishyfish777
- Start date
Ah, that makes sense. I still hadn't bothered replacing the acorn nuts due to the fact that the engine was running well aside from the loss of power, but I guess I'll replace the acorn nuts with the four extra lock-washers I bought for that purpose now. Thanks!
I hate to keep posting, but since you still using the acorn nuts, here we go again.
These are the things that I do, I see that others such as the seals (which I've never had one go bad) mentioned. All these mods or replacements are most likely less then $50.00. Choose what works for you, ignore the rest, but here you have them.
1. Unpack engine
2. Check for any missing parts
3. Remove head
4. Mill head (flat glass and 230 (or finer) grit sand paper. Rub gasket surface to insure it is flat. Check the cylinder also.
5. Tap cylinder stud holes to insure they are taped to the bottom.
6. Discard all cylinder/ intake, exhaust and mounting studs and nuts.
7. Replace studs with Metric 8.8 (US Grade 5) Replace nuts with locking nuts. 8mm studs are either 1.0 or 1.25 thread, 6mm studs are 1.0 thread. 8mmX1.0 is not common, but I have 1 engine with them.
8. Replace spark plug with a NGK or the like.
9. Replace spark plug wire and boot (check with lawnmower supply) or rob from old lawnmower. Use wire core lead.
10. Mount the engine properly, no gaps between the bike tubes and engine mounts.
11. Torque 8mm to 150 to 200 INCH POUNDS
12. Torque 6mm to 60-70 INCH POUNDS
13. I install cylinder studs with lock tite, and let set overnight
14. I spray the head gasket with Copper Kote, both sides twice
15. May need to bend exhaust pipe for crank or frame clearance. Recommend using heat.
16. Remove or cap magneto white wire off.
17. Re solder blue wire on magneto.
18. Make sure all wires have a good connection and use tape or better yet shrink wrap.
19. Hook up kill wires AFTER you get engine running.
20. Try not to drill holes in the bike frame.
21. Do away with the clutch cable routing; there are a number of options.
22. On my kit the rag joint had gauge (Metric) 8.8 bolts, If not replace them. I replaced the nuts with lock nuts.
23. I sealed the wires coming from the magneto out of the engine with RTV.
24. Place a “O” ring in the carburetor throat.
25. Some say replace the axle with a better one. Never had a axle bend on me.
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I experienced a similar power loss once . I traced mine to the CDI going out. My CDI was actually just a tiny bit little warm to the touch from shorting out internally. Do check the simple stuff first like properly torquing the head.
Yeah, I milled the cylinder head flat, properly torqued the head bolts with new nuts and all that but oddly it's still repeating the process - at full throttle ten minutes after starting, it barely moves around 10 miles an hour (heavily four-stroking all the while.) Throttle response is okay so it's definitely not an air leak of any sort, fuel flow is okay, and I just replaced the spark plug with the proper NGK equivalent so it's not the spark plug, either - must be something electrical. I'll check out the CDI and magneto.
Sorry for the extremely blurry shots, I couldn't find my camera so I had to resort to my iPod Touch.
Upon a visual inspection, the magneto coil looks fine and my screwdriver stuck to the magnet so that's fine too. The wires leading up to the CDI are soldered and then taped over and then taped using electrical tape to the frame - there shouldn't be much problem with that since the engine fires up nicely. I don't really know how to disassemble the CDI, however, so that remains stuck to the frame.
Aside from the CDI, what could possibly be the problem - and if it is the CDI, how do I fix it (preferably without having to bother with more prepaid cards and buying stuff off the internet)?
Upon a visual inspection, the magneto coil looks fine and my screwdriver stuck to the magnet so that's fine too. The wires leading up to the CDI are soldered and then taped over and then taped using electrical tape to the frame - there shouldn't be much problem with that since the engine fires up nicely. I don't really know how to disassemble the CDI, however, so that remains stuck to the frame.
Aside from the CDI, what could possibly be the problem - and if it is the CDI, how do I fix it (preferably without having to bother with more prepaid cards and buying stuff off the internet)?
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Nah, it actually four-strokes more and more as it warms up so I don't think lack of gas is the issue.
Heavily four stroking?
By definition, that would mean it's running too rich.
Re-jet the carby.
rc
By definition, that would mean it's running too rich.
Re-jet the carby.
rc
Here's some crazy questions... How are you mixing your gas & oil?, what plug are you using & whats the gap set at??
I also concur... get rid of that blue tape!! Solder & heat shrink the wires & don't bind them too tight to the frame.
I also concur... get rid of that blue tape!! Solder & heat shrink the wires & don't bind them too tight to the frame.
The only thing I can think of is ring end gap being too tight and loosing compression when hot, but this seems extremely unlikely to me. I'd try the cdi box first and see what happens.
Check the rings and cylinder wall next time you have the head off.
Check the rings and cylinder wall next time you have the head off.
four-stroking isn't a defined symptom of being rich, having a 19mm carb when it four strokes I can just open the throttle up more and it'll stop. The way I told my girlfriend to ride it: If it four strokes, give it more gas. If it bogs, give it less. It's a breathing problem inherent to the engines design, but four-stroking is a sign that the mixture isn't right. If you're too lean, then it simply wont fire, and if it does you risk detonation, because each subsequent intake will just bring more air in and keep the mix improper. Rich four-stroking is much more common.
If it's four-stroking at your top speed, try turning the gas off. If it suddenly stops four-stroking and goes nuts fast for a couple seconds before dying, then yes, you're too rich. If that doesn't happen, then it's a breathing issue. Changing up your port timing can help, getting a bigger intake can help as well, better transfer efficiency (boost port will help a LOT, but you need reed valves, my black bike doesn't four-stroke at all, it runs reeds) so on and so on.
However if you're just experiencing a power loss as the engine warms up and it's NOT four-stroking, try playing with the choke at various positions, you could be too lean and need to jet up. I wrote a rather long post in my signature ("Stop four-stroking!") that explains what's going on inside the engine as it does this.
If it's four-stroking at your top speed, try turning the gas off. If it suddenly stops four-stroking and goes nuts fast for a couple seconds before dying, then yes, you're too rich. If that doesn't happen, then it's a breathing issue. Changing up your port timing can help, getting a bigger intake can help as well, better transfer efficiency (boost port will help a LOT, but you need reed valves, my black bike doesn't four-stroke at all, it runs reeds) so on and so on.
However if you're just experiencing a power loss as the engine warms up and it's NOT four-stroking, try playing with the choke at various positions, you could be too lean and need to jet up. I wrote a rather long post in my signature ("Stop four-stroking!") that explains what's going on inside the engine as it does this.
You already have a thread asking this question. You'll get better response if you don't multiple/duplicate your questions in several areas. That is considered poor forum etiquette. Refer to the responses you have recieved in your thread.
Tom
