Why does everyone hate 4-stroke bikes?

[DAMIEN1307]

In my dreams

You must have gotten ahold of some of the "inspectors" private stash...lol...lol.

 

[noah9988]

WHY???...lol...The OP did ask "why does everyone hate 4 strokes"...I think your giving some good reasons why you hate 4 strokes...lol.

Mainly because I want advice on what to troubleshoot, which would create more replies. But basically I have a mikuni round slide (not sure what size), a 30mm pwk and a 21mm pwk that I've tried with various jets. I have had the original and pvl aluminum flywheel. I've tried the stock rusty coil and a new stock coil from arc racing. With any of these combinations it would not rev over 6400 rpm, even with a cm grind cam and 22 lbs springs.

The spark plug (which I have also tried various of) is a light brown although I have much less experience with 4 stroke plugs it seems fine. It randomly cuts out while cruising at part throttle, like it just doesn't fire for some reason and jerks you forward. On the top end it's not revving out smoothly but rather kinda jittery or stuttering. I suspect the coil or coil gap. If it's not coil related I'm out of ideas.

 

[Sidewinder Jerry]

I will build a 4-stroke one day... but frankly... my biggest beef with 4-strokes...


They are ugly. The engine is just... ugly. I don't care what brand... I don't care what you strip off of it... they're just ugly.


A 2-stroke engine just looks more like what you'd expect to see in a motor-bike... rather than what you'd expect to see in a "mini bike".

I think my little Robin is pretty.

 

[darwin]

I thought it was the Sam Elliot aura, at least that's what the chicks tell me

In my Dreams I feel like John Wayne Clint Eastwood and Sam Elliot all rolled into one, Then I wake up disappointed

Brad Pitt here, Looked my worst in the movie Troy.

 

[Karl Snarl]

Mainly because I want advice on what to troubleshoot, which would create more replies. But basically I have a mikuni round slide (not sure what size), a 30mm pwk and a 21mm pwk that I've tried with various jets. I have had the original and pvl aluminum flywheel. I've tried the stock rusty coil and a new stock coil from arc racing. With any of these combinations it would not rev over 6400 rpm, even with a cm grind cam and 22 lbs springs.

The spark plug (which I have also tried various of) is a light brown although I have much less experience with 4 stroke plugs it seems fine. It randomly cuts out while cruising at part throttle, like it just doesn't fire for some reason and jerks you forward. On the top end it's not revving out smoothly but rather kinda jittery or stuttering. I suspect the coil or coil gap. If it's not coil related I'm out of ideas.

Have you changed your spark plug? Try a different brand. Try an all copper cheapo autolite plug, or a champion. The main reason we use those fancy plugs, they last a long time. All of these plugs should in theory out last our bikes. Anyway, try a copper core, nickel plated marine plug if you want super duper longevity of the plug ( they only cost a few bucks), or just a use a cheap champion etc, copper core plug. The copper core plugs are the best for transferring energy, hands down. They just don't last as long as rare earth metal plugs. Could be the spark can't keep up with the charge, light brown is the color. Could be a loose wire making ground, etc.

 

[darwin]

I'm thinking here, dangerous I know. Seems a proper spark plug color chart for plug condition should be different for 4 strokes vs 2 strokes. Way more oil in the combustion chamber has to make a difference. What's your thoughts?

 

[DAMIEN1307]

Have you changed your spark plug? Try a different brand. Try an all copper cheapo autolite plug, or a champion. The main reason we use those fancy plugs, they last a long time. All of these plugs should in theory out last our bikes. Anyway, try a copper core, nickel plated marine plug if you want super duper longevity of the plug ( they only cost a few bucks), or just a use a cheap champion etc, copper core plug. The copper core plugs are the best for transferring energy, hands down. They just don't last as long as rare earth metal plugs. Could be the spark can't keep up with the charge, light brown is the color. Could be a loose wire making ground, etc.

Have you been smoking a 'not so rare earth' type of vegetation this evening Karl???...lol...lol.

You DO realise that the NGK-BR6HS standard plug we pretty much all use here is also a copper core too???...lol...Most of us are NOT using any 'rare earth' plugs...lol.Just saying...lol...lol.

https://www.oreillyauto.com/detail/c/copper-core/ignition---tune-up/spark-plug/b14eb31b13d7/ngk-copper-core-plug-number-br6hs-spark-plug/ngk1/3922

 

[noah9988]

Have you changed your spark plug? Try a different brand. Try an all copper cheapo autolite plug, or a champion. The main reason we use those fancy plugs, they last a long time. All of these plugs should in theory out last our bikes. Anyway, try a copper core, nickel plated marine plug if you want super duper longevity of the plug ( they only cost a few bucks), or just a use a cheap champion etc, copper core plug. The copper core plugs are the best for transferring energy, hands down. They just don't last as long as rare earth metal plugs. Could be the spark can't keep up with the charge, light brown is the color. Could be a loose wire making ground, etc.

I mainly tried a champion rn9yc and a ngk bpr5es. I also have some various other plugs that don't have enough reach like a br8hs and some e3's though I didn't try them. I'm not sure if it's floating the valves but the cam recommends 20 pound springs. It's currently not running and I have to wait for parts later in the week but that's unrelated. It's a used engine with very little time on it, but it has had water in it. The bore has light rust staining and a ring at the bottom of the bore with pitting. I've since honed it. I also ordered a new vm22 carb. If I still can't figure it out I'll make a separate post about it.

 

[DieselTech]

I mainly tried a champion rn9yc and a ngk bpr5es. I also have some various other plugs that don't have enough reach like a br8hs and some e3's though I didn't try them. I'm not sure if it's floating the valves but the cam recommends 20 pound springs. It's currently not running and I have to wait for parts later in the week but that's unrelated. It's a used engine with very little time on it, but it has had water in it. The bore has light rust staining and a ring at the bottom of the bore with pitting. I've since honed it. I also ordered a new vm22 carb. If I still can't figure it out I'll make a separate post about it.

What CM grind camshaft are you running, what is the lift? I think the 22lb springs are too weak for them kinda of rpms you are turning. I would go 26lb or heavier on the springs. Then get a autolite AR3910X spark plug. Let me know your build specs. Then I can give you some more info.

 

[noah9988]

What CM grind camshaft are you running, what is the lift? I think the 22lb springs are too weak for them kinda of rpms you are turning. I would go 26lb or heavier on the springs. Then get a autolite AR3910X spark plug. Let me know your build specs. Then I can give you some more info.

Recommended Class:	Super Stock
Target (MAX) RPM:	7500
Spring Pressure (In / Ex):	20 lbs
Valve Lash (In/Ex):	.003"
Ignition Timing:	32 Deg BTDC

​

	Intake	Exhaust
Open:	52.4 BTDC	86.9 BBDC
Close:	89.4 ABDC	51.5 ATDC
Lift:	.265"	.265"
C/L:	108.0 ATDC	108.0 BTDC
DUR @ 50:	236.9 Deg	236.5 Deg

That's the specs for the cam. It's a hisun 196cc shaved and ported head, header pipe with muffler, 22 lbs springs, pvl aluminum flywheel with 4 degree offset key for 32 degree timing. I bought a new stock coil and put an ngk boot on it with an ngk bpr5es plug. One thing that could be off is the coil gap which I set at .060". I have also lapped the valves and set the clearance at .003".