200-300 Miles into riding smooth now have four stroking occuring

DJDeSio77

New Member
Jun 10, 2020
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Rhode Island
Hey everyone, new to the forum but joined because of this issue i am having, so my bike has about 200-300 miles on it. it ran AMAZING for those first few hundred miles top speed 32mph on flat ground stock sprocket, carb needle set as rich as possible, and never had an issue with four stroking, always ran great at WOT (wide open throttle). suddenly on the way home from a 30 mile ride the other day i noticed the bike lost some throttle response especially at WOT or top speed, then started listening and it is four stroking HARD but only in the high RPM range under load. I pulled the carb needle and adjusted it as lean as it would go and it helped slightly but not much and now ive lost high RPM power only running around 22mph on flat ground with WOT. i also pulled the spark plug and wire brushed it to no avail. any suggestions as to why all the sudden my bike is four stroking so much?
 

DJDeSio77

New Member
Jun 10, 2020
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Rhode Island
Longshot, but you might try it without the air cleaner. If that's restricting it could be acting like a choke.
I was thinking that too. It's raining today but tomorrow I'm going to try pulling the air filter off and cleaning it... any chance my stock exhaust could be clogged up? Or is that not a thing?
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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up north now
Clean the filter, get a NEW NGK plug, and be very consistent with your fuel/oil ratio.

If you were running the dreaded 16:1 ratio, and you changed to a proper 32-40:1 mix, that will make it run rich.
 

DJDeSio77

New Member
Jun 10, 2020
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Rhode Island
Clean the filter, get a NEW NGK plug, and be very consistent with your fuel/oil ratio.

If you were running the dreaded 16:1 ratio, and you changed to a proper 32-40:1 mix, that will make it run rich.
Ok so I did do the 16:1 for the first 100 miles or so, but have been running 32:1 for a while now. And at the beginning of this 30 mile ride (probably the first 20 miles) it ran fantastic. Then it started to four stroke when I would try to get it to the high rpms to pick up speed. I'll continue to run 32:1 and look into a new plug. Will any NGK plug work?
 

DJDeSio77

New Member
Jun 10, 2020
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I'm with Joe & FOG... Clean the air filter & try some fresh gas. Use a NGK~B6HS (#7534 on the box)
I will be cleaning the filter today, if i have time i will run to autozone and try to grab a new plug. i have a new NGK BR8HSA hanging around but im not sure what the difference between the B6HS and the one i have is? is it spark temp? Gap size? either way i will update the thread this afternoon withg results. Thanks guys
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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Los Angeles, CA.
I will be cleaning the filter today, if i have time i will run to autozone and try to grab a new plug. i have a new NGK BR8HSA hanging around but im not sure what the difference between the B6HS and the one i have is? is it spark temp? Gap size? either way i will update the thread this afternoon withg results. Thanks guys
That #8 plug runs much colder than a #6 (& will foul with oil)... The #6 will run the best.
 
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DJDeSio77

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So the problem did end up being a clogged air filter. Loaded with oil sludge. Cleaned that and moved the needle to a more lean condition and she ran great! Thanks for the help everyone... now for the bad news. While on my test ride I somehow managed to run over some rope which worked it's way around my rear breaks dragging them into the spokes causing the rear break caliper to bend severely and ripping out 4 spokes wrapping them around the axle. The bike is from 1970 it's a huffy regatta. Parts are tough to find and the rear wheel is a 3 speed hub transmission. I'm still trying to decide if I want to put the work into fixing this 1970s huffy or just go buy a new frame for this engine. I'll attach a picture of the bike before the damage so we can mourne its loss together lol
 

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Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
6,783
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Los Angeles, CA.
I'm glad the engine problem was easy to fix... But bummer about the bike... :(

Unless you can do the repairs yourself?, it might be cheaper to just buy another used bike from your local thrift store or craigslist.
 
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Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
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up north now
So the problem did end up being a clogged air filter. Loaded with oil sludge. Cleaned that and moved the needle to a more lean condition and she ran great! Thanks for the help everyone... now for the bad news. While on my test ride I somehow managed to run over some rope which worked it's way around my rear breaks dragging them into the spokes causing the rear break caliper to bend severely and ripping out 4 spokes wrapping them around the axle. The bike is from 1970 it's a huffy regatta. Parts are tough to find and the rear wheel is a 3 speed hub transmission. I'm still trying to decide if I want to put the work into fixing this 1970s huffy or just go buy a new frame for this engine. I'll attach a picture of the bike before the damage so we can mourne its loss together lol
I have a 3 speed wheel from a 70's Schwinng Collegiate I would trade for a guitar......
 
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DJDeSio77

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Jun 10, 2020
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Hey guys. So I moved the motor over to a decent steel frame aluminum wheel mountain bike. Brakes are way better and dirt trails are a blast. After cleaning the air filter and moving the engine to the new bike frame the motor ran better than ever. It screamed at 34 mph on flat ground. After riding about 10-15 miles running great I parked it for the night and forgot to shut the gas off. Woke up the next day and I the engine was flooded. Cleaned the air filter again but it still seems to be 4 stroking even after riding 30 miles to try to burn off the excess flooding. Do I need a new carb? Is my float just crappy and keep getting stuck because of the vibration? Suggestions on new carbs would be very helpful. I live in Rhode island at sea level.
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
241
63
up north now
The float may have a tiny bit of crud in the float valve seat. I say this because if you left the gas on, the float should have shut off fuel to the carb. Take a close look at the floats while you have it apart, and see if there is fuel inside- it happens.
 
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DJDeSio77

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Jun 10, 2020
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The float may have a tiny bit of crud in the float valve seat. I say this because if you left the gas on, the float should have shut off fuel to the carb. Take a close look at the floats while you have it apart, and see if there is fuel inside- it happens.

I will definitely be taking the carb apart tomorrow to take a look. With all the dirt trail riding I did I'm wondering if the stock air filter isnt sufficient with all the dirt and dust being kicked up by the back wheel causing float problems. I'll clean the carb up and if it happens again I may look into a different filter medium that I can still use on the stock carb. Any other input is always welcome thanks for being so responsive!
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
6,783
704
113
Los Angeles, CA.
Hey guys. So I moved the motor over to a decent steel frame aluminum wheel mountain bike. Brakes are way better and dirt trails are a blast. After cleaning the air filter and moving the engine to the new bike frame the motor ran better than ever. It screamed at 34 mph on flat ground. After riding about 10-15 miles running great I parked it for the night and forgot to shut the gas off. Woke up the next day and I the engine was flooded. Cleaned the air filter again but it still seems to be 4 stroking even after riding 30 miles to try to burn off the excess flooding. Do I need a new carb? Is my float just crappy and keep getting stuck because of the vibration? Suggestions on new carbs would be very helpful. I live in Rhode island at sea level.

After cleaning the carb as Joe suggested, (if that doesn't fix it)?, try installing a new spark plug
 
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DJDeSio77

New Member
Jun 10, 2020
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Rhode Island
Cleaned out the carb today. Didnt notice anything in the float valve seat. Still running too rich and 4 stroking on leanest carb setting. Which I would have thought would be plenty lean enough especially at sea level. Going to call up napa today and try for a hotter spark plug as suggested earlier. The plug I'm using is the stock plug with 2 or 300 miles on it. Fingers crossed this solves my issue.
 

DJDeSio77

New Member
Jun 10, 2020
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29
Rhode Island
After cleaning the carb as Joe suggested, (if that doesn't fix it)?, try installing a new spark plug

So I bought a new NGK BR6HS... it stopped the 4 stroking!! But... still felt a lack of power at high rpms.... felt like it was being choked.... so I looked back at the air cleaner and realized I tightened the screws too far pushing the plastic flat against the intake choking it out. STUPID MOVE so I back the screws out a bit, and now she runs nice. I'm about 215lbs and it will keep me going around 34mph on flat ground. Fantastic! Thanks for all your help guys!