Strange noise preventing power

[Chriskelly]

I've got the air filter of until I get a chance to modify the intake as my frame is small and won't fit,took the bike to work this morning and had trouble with it bogging out when I pulled the throttle but after tweaking the choke it started to go properly bit still with the noise,the noise did stop for the last minute of my ride so will update later on my way home to see what the situation is

 

[Chriskelly]

Also I have cut my baffle and taken 1ml of the circumference of the muffler outlet pipe on cap

 

[Chriskelly]

Update! On my way home today the noise/four-stroking was still there for about five minutes then stopped once engine got hot! Is that four-stroking?

 

[Deleted member 12676]

a cold engine likes a rich mixture more than a hot engine

 

[zippinaround]

by air flapping do you mean like a popping noise? if it sounds like air coming from somewhere it probably is the head gasket , when the engine gets hot the metal expands closing the gap? just my thoughts if it is the head you should see an oil mark where its blowing out

 

[Chriskelly]

Hmm,thats odd as I was sure I was running rich but it does seem to be sounding and performing better now once it's been run for five minutes and engine is warmed up,i have another carb in the shed going to try that as a comparison to see if it runs better or worse with the jets on that one

 

[Chriskelly]

It's definitely not the head,i had a bolt snap on my first after over tightening due to in experience and rode it for days before I got the new parts,had to for getting to work lol,the new engine has just had the head changed from a punch to a slant head for better frame clearance and is perfectly sealed,although I do plan on using a thinner gasket at some stage

 

[Chriskelly]

Tried the other carb I have! It bogged out and died every time I started it,so back to the old carb

 

[Chriskelly]

Update! I swapped the jets as one was shorter so my theory was the needle would be more restrictive, worked a treat no four-stroking at full throttle,bike is slightly slower at acceleration but hits higher top speeds (37mph) on my short test run and sounds much better next step is to re shape the intake so I can fit my carb cover on

 

[CrazyDan]

Make sure after each adjustment you make to the engine to tear it around the block and come hauling butt up to your house, killing it while at wide open throttle. Then check your sparkplug to see how your engine is running. White=lean, black=rich, brown=just right. I prefer a darker brown to a lighter brown, slightly rich runs a little cooler with not much power loss. Slightly lean can be snappier but tends to run hotter. Nice to see you've solved the issue .