Motor Fires but no power

Matthew Johnston

New Member
Dec 5, 2019
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Hello, I am new to the motor bicycling world and I have no idea what the problem would be here. I have a flying horse 66/80cc 2 stroke kit. I built it and it worked fine for the first ride then started to have small problems that I fixed. After that, I went to take the bike out and ride it and now it fires up and throttling reves the engine but I'm not getting any power to the wheel. I have no idea where to start with this problem any help would be amazing. Thanks
 

Matthew Johnston

New Member
Dec 5, 2019
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No pull start its hold clutch pedal get up to speed release clutch motor starts then it dies because there no power going to the wheel even when i give it gas and the engine revs up more.
 

Greg58

Well-Known Member
May 1, 2011
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It sounds like you hear the engine turning over but it is not running, the first thing to do is check for fire. Remove the spark plug and connect it to the cdi and hold it on the head, now walk the bike with the clutch out, as you hear the engine turning you should see fire at the plug.
 

Goblin

New Member
Dec 29, 2019
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Hey everyone im kind of new on here and i wanted to see if i could get some troubleshooting help on my new 2 stroke build.

I have a flying horse 2 stroke engine that i am breaking in and I am running a 50:1 mix ratio. The engine and everything are brand new and haven't been fully broke in yet. Also, my carb is an NT carb. My issue is that I feel like I am loosing power when i ride and i cant tell if its because the engine isn't worn in yet or because its another issue. I suspect another issue. The Bike starts well and runs fine but lacks power (only 10 mph or less) and it struggles on even small hills. I have adjusted my idling screw and needle clip (tried and tested every groove) and have drained my tank and added new fuel. Based on my plug chops and testing to see if the spark plug is oily or dry then it looks like my mix is fine so I am kind of stumped on what to do from here. I had a previous engine that was on a build i bought and it was really fast and ran great like it should have so i am wondering if it was because it was already broken in or if it could be something else like the jet. No idea what jet is in the new engine. i was thinking of possibly cannibalizing the other jet off the old motor since its busted ( mounting studs broke and block broke when i tried to dig them out. I am pretty mechanically inclined so I am willing to experiment a little. Everything on my new engine is stock.
 

DXZeff

New Member
Dec 12, 2019
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@Matthew Johnston As Greg suggests, check for spark, whilst doing so it might not hurt to try gently turning the lead clockwise in the CDI, the wire literally just goes over a screw and mine came loose after I'd had it disconnected once, though in my case it manifested as what sounded like 4-stroking.

I'm guessing you tried starting with the choke lever in different positions? As the weather changes the position it wants to be in to get the motor running will also vary.

If going down that route leads you nowhere, my next stop would be the carb, I guess, such as making sure the air cleaner isn't clogged up, that there isn't a load of crud or varnish in the bowl or blocking the jet. Beware that if you take the bowl off the bottom, you might have to replace the gasket depending on how long its been there.
Similarly if you find that spark and fuel aren't the problem, and if you find that the air cleaner has been getting blasted with oil, there may be a buildup of crud in the exhaust, but you probably will have to replace the exhaust gasket if you take that off to clean it, as they usually leak slightly if you put it back on with the old one.

@Goblin Evidently you saw my thread. As my motor is retiring in the next week or so, I've been tampering with it and found a few things in the process. Firstly, due to the load on my engine I run more oil than most here, but I did discover that lowering the amount of oil actually makes it perform worse and have some theories as to why.
It may be worth dumping more oil into your gas, maybe double, and giving it a try, maybe when you're at half a tank so you can always dilute it with gas again if it ends up making things worse and want to go back to the old mixture. Obviously you might have to play with the needle again to make it run right with the increased oil. Whilst I don't remember the exact science behind it, the fuel I have access to is known to be trouble and there's some relation somewhere between octane level and engine compression, as this is an engine with fairly low compression my guess is that the oil is somehow making the fuel more or less stable in some way, because if I use less of it the engine runs worse, at 50:1 I would be hearing constant pinging, at 24:1 the engine performs horribly, as I approach 16:1 it improves, though if I keep adding more oil beyond that it starts to run worse and smoke like it's running on coal, as one would expect. Once I have the new bike and engine, I may try using different fuel in this one to see what effect it has.
Secondly, I discovered that the gasket for the intake port was impeding said port slightly, I took a spare which would also have done this, but made the hole larger, so that it was the same shape and size as the port on the cylinder, whilst this didn't gain any more speed, it did make the engine kick noticeably harder when accelerating and make achieving the top speed much easier to do. It seems that between that and slowly drilling out the baffles slightly, I did at least gain more torque if nothing else.

- Of course, I'm not expert in these matters, so you should fully expect my ramblings to lead you nowhere, especially as my engine is a cheap piece of trash made up of parts from two different versions and running on sub-par gas, who knows how much this has skewed my observations.
 
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Goblin

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Dec 29, 2019
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Welcome to the forum Goblin, if the two carburetors are the same swapping jets might help, or you can use the old carb as it is to test.
So originally the NT card is from the old engine the new engine came with a "High Performance" carb but the issue i had with it is that it doenst use a needle and clip and you cant tune it. it relies soely on an idle screw and jetting. so for that one i decided to just foget that ang go stock since im more familliar and dont really want to get into a whole lot of jetting if i can avoid it.
 

Goblin

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Dec 29, 2019
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So to clarify i am guessing that since i am having an issue still even when im using the old carb (working jet) then im wondering if its and air or fuel issue. Ill probably dismantle everything later and just do an entire walk through so i can say that i officially checked everything. What recommendations do you guys have for tourque specs on the head bolts? i was thinking around 8-10 ft lbs.
 

Greg58

Well-Known Member
May 1, 2011
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10lbs on 6mm studs, 12lbs on 8mm. Be sure to true the head surface if you take it off, use sandpaper taped to a flat surface and sand in a circular motion. Most every head will seal better after.
 
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