Too hot?

[ishman]

My Tachometer finally showed up yesterday, took it out for a run and the top RPM's it shows is 3780, stock carb, aftermarket pipe, valves adjusted, NGK iridium plug . OK I am 250 lbs, the bike has a 44T cog and 26x 2.35" Fat Frank tires. Is this normal rpm's? I dont have a speedo, mine took a dump, another is on the way, so I dont know what speed, but it doesnt feel like 30mph.

Any thoughts?

Ishman

 

[sbest]

3780 rpm sounds about right for a utility 4 stroke engine. Most are unable to go over 5000 rpm without significant modification. Lower rpm makes for a tougher motor but limit the power potential, balanced of course by the 4 stroke's typically greater efficiency.

Steve

Edit: Above statement does not apply to this engine.
I stand corrected and resolve to not wade in to unknown waters.

 

[ishman]

OK, at least Im not beating my head against a wall trying to achieve something that isnt there to start with.
We'll call it a baseline.

Ishman

 

[FFV8]

You are lugging the engine.

Here is the power curve:

 

[Agreen]

Absolutely. If your transmission is a 4:1 ratio with a 9t output driving a 44t sprocket, using a 26x2.35 tire at 3780 rpm, that's 15 mph. Something's not right there.

Can it free-rev higher than 3780?

 

[MotorBicycleRacing]

My Tachometer finally showed up yesterday, took it out for a run and the top RPM's it shows is 3780, stock carb, aftermarket pipe, valves adjusted, NGK iridium plug . OK I am 250 lbs, the bike has a 44T cog and 26x 2.35" Fat Frank tires. Is this normal rpm's? I dont have a speedo, mine took a dump, another is on the way, so I dont know what speed, but it doesnt feel like 30mph.

Any thoughts?

Ishman

You have the Tach on the wrong setting so it is reading half the RPM's.
3780 x 2 = 7560 RPM

Your 4 stroke waste fires so it sparks the same as a 2 stroke.

 

[ishman]

I have the tach set for a 2 stroke engine, since I had read about the waste spark situation earlier. I will recheck the tach, but it was reading around 1100rpm at idle. Do these normally idle around 2200rpm?
Im no noob, Ive been around all kinds of engines for more than 40 years, something is up with engine. It was crummy when I started with the NT carb, better with the SHA, even better once I got the stock carb to fit in the frame. But there is still something holding this thing back I will recheck the tach settings tomorrow.
Thanks for the help guys.

Ishman

 

[KCvale]

My Tachometer finally showed up yesterday, took it out for a run and the top RPM's it shows is 3780, stock carb, aftermarket pipe, valves adjusted, NGK iridium plug . OK I am 250 lbs, the bike has a 44T cog and 26x 2.35" Fat Frank tires. Is this normal rpm's? I dont have a speedo, mine took a dump, another is on the way, so I dont know what speed, but it doesnt feel like 30mph.

Any thoughts?

Ishman

Max power is achieved @6800rpm 1.2KW.
Clutch engagement is ~3500.

You just have your tach in the wrong mode ;-}

Save​

 

[ishman]

OK once in a while, one must eat their words, and with chinese electronics I AM a noob. I have attached a pic of the Tach settings table. Now, I have the tach set to the first position (2 stroke 1 cylinder), would this not be correct?

Ishman

 

[MotorBicycleRacing]

OK once in a while, one must eat their words, and with chinese electronics I AM a noob. I have attached a pic of the Tach settings table. Now, I have the tach set to the first position (2 stroke 1 cylinder), would this not be correct?

Ishman

2nd position is correct.

"2 stroke" does not mean a 2 stroke motor.
It means literally 2 strokes up and down of the piston before it sparks.

Your idle speed being half what it should be should be a clue.

 

[ishman]

Well there you go. Hopefully it stops raining around here tomorrow so I can take a ride with the correct settings. I will post my results.

Thx.

Ishman

 

[KCvale]

2nd position is correct.

"2 stroke" does not mean a 2 stroke motor.
It means literally 2 strokes up and down of the piston before it sparks.

The thing is you are measuring full engine rotation by when the plug fires.
A 4-stroke normally does 2 rotations before the spark fires, but most of these engines fire the plug on the exhaust/intake stroke so each rotation is counted.

2nd setting.

 

[ishman]

I have the tach in the second position now and it reads that the engine idles at 2200rpm and clutch engagement at 4000rpm. Still havnt rode yet but Im sure it will read 3750rpm x 2 (7500rpm), so if that is the case Im in the pink, right? From all the postings I have read about performance expectations, No problem!
I am anxious to se what speed I am getting, feels like between 25 - 30mph.
Im amazed at how far off I was on the rpms this motor was turning. I am a 55 year veteran of Detroit, working in the industry and on everything with an engine: mini-bikes, mopeds, dirt bikes, 4 wheelers, snowmobiles, outboard motors, jet boats and many muscle cars. I swear this motor is smoother than either of my Honda CT-90's.


Ishman
.

 

[KCvale]

I have the tach in the second position now and it reads that the engine idles at 2200rpm and clutch engagement at 4000rpm. Still havnt rode yet but Im sure it will read 3750rpm x 2 (7500rpm), so if that is the case Im in the pink, right? From all the postings I have read about performance expectations, No problem!
I am anxious to see what speed I am getting, feels like between 25 - 30mph.

Im amazed at how far off I was on the rpms this motor was turning.
I swear this motor is smoother than either of my Honda CT-90's.

As mentioned, the sweet is spot for power is 6800rpm. for torque it is 4500rpm. Keep it under 7500rpm!

The HS 142F is a near exact part for part knock-off of the Honda 50, but a darn good one for ~$50 less.

25-30mph is about right for direct drive.
Put on a new exhaust, air cleaner, and NGK 7544 (CR7HIX) Iridium spark plug in and you'll feel a bit of a boost.

I have been using a few HS 144F-1G 53cc engines of late.
You wouldn't think 4cc would make a lot of difference but it does.
Heck just the slightly longer NGK plug increases compression enough to feel.

Let the 144 breath and use the bike gears and you got some machine.

0-25mph in like 4 seconds, 45mph in under 10 seconds.

Its amazing what you can get out of a little 2hp engine and gears.

Just run it between 4500 and 6800 RPM's, that is the torque and power sweet spots, and use the gears for balancing power for conditions, that tach will help with that even on a direct drive, so will the engine hours display, change your oil after test riding for 1 hour, then 10 hours, then every 50 hours.

Hope that helps ;-}

Save​

 

[ishman]

I have refered to this engine as 49cc a few times, but in actuallity it is the 53cc HS-144 model.
Just for review, I have installed a Long Shot exhaust pipe from Bikeberry, an NGK-7544 plug, I am using the stock carb (stock settings) and adjusted valve lash to correct .004" int.- .006" exh.. Top RPM attained was 7560 and seems to be going between 25-30mph. Souns like Im looking for something that is already there. Before getting this tachometer, I wouldn't have thought this engine was attaining these rpm's. It dose not sound like it is "winding out". I was thinking maybe, because it is an OHV design, but I have a 7HP Tecumseh lawn mower and a 30cc Ryobi weedwhacker, both OHV and both sound to my ear, like they are spooling up to faster clicks than the HS.
Well Im done over thinking it. Once the speedo comes in, I will post top and crusing speeds, for reference.

Ishman

 

[curtisfox]

As mentioned, the sweet is spot for power is 6800rpm. for torque it is 4500rpm. Keep it under 7500rpm!

The HS 142F is a near exact part for part knock-off of the Honda 50, but a darn good one for ~$50 less.

25-30mph is about right for direct drive.
Put on a new exhaust, air cleaner, and NGK 7544 (CR7HIX) Iridium spark plug in and you'll feel a bit of a boost.

I have been using a few HS 144F-1G 53cc engines of late.
You wouldn't think 4cc would make a lot of difference but it does.
Heck just the slightly longer NGK plug increases compression enough to feel.

Let the 144 breath and use the bike gears and you got some machine.

0-25mph in like 4 seconds, 45mph in under 10 seconds.

Its amazing what you can get out of a little 2hp engine and gears.

Just run it between 4500 and 6800 RPM's, that is the torque and power sweet spots, and use the gears for balancing power for conditions, that tach will help with that even on a direct drive, so will the engine hours display, change your oil after test riding for 1 hour, then 10 hours, then every 50 hours.

Hope that helps ;-}

Save​

What is your finial gear ratio................Curt

 

[ishman]

Not sure on the math but, it has the 5:1 trans and 9T / 44T sprockets, 4.8:1.
Should it fall in between the two? 4.9:1?

Ishman

 

[curtisfox]

Not sure on the math but, it has the 5:1 trans and 9T / 44T sprockets, 4.8:1.
Should it fall in between the two? 4.9:1?

Ishman

Wanted to know what KCvale has for ratio. LOL Thank you, I should of put KC in front of my question.
ishman i think your ratio is to high, going to wear out the clutch and parts fast.....Curt

 

[KCvale]

I have refered to this engine as 49cc a few times, but in actuallity it is the 53cc HS-144 model.

Sweet, I like the 53cc edge.

Sounds like you are getting drag somewhere, what are using for a transfer case?

Save​

 

[ishman]

I put the bike on the kick stand today and pegged the throttle, no load RPMs through drivetrain were 7560. Transfer case is the 4G - 20T/100T (see uploaded pictures) Im using the 9 T drive sprocket off of the transfer case going to a 44T sprocket on the wheel, if the ratio is too high right now, where does it need to be? What wheel sprocket size would be needed then to bring it to the correct final ratio. What is the correct final ratio using 26" wheels with 2.35" tires?

Ishman

 

[KCvale]

I put the bike on the kick stand today and pegged the throttle, no load RPMs through drivetrain were 7560.
Transfer case is the 4G - 20T/100T (see uploaded pictures)
Im using the 9 T drive sprocket off of the transfer case going to a 44T sprocket on the wheel'.
What is the correct final ratio using 26" wheels with 2.35" tires?

Ishman

[FONT=Verdana, Arial, Helvetica]To travel one mile a 26" wheel requires 775.5 wheel revolutions.
That is the 'magic number' you have been missing for your speed math.

Your 4G transfer cases 20T/100T reduction is 100/20=5:1
Your 9T engines output to 44T wheel sprocket is 44/9=4.9:1 multiplied reduction.
5*4.9= ~25:1 for your total reduction to your wheel.
[/FONT]
@6800rpm your back wheel would spin 6800/25=272rpm.
Speed is measured in time so now we convert rotations per minute to hours.
272*60= 16,320 rotations per Hour.

Now that magic number...
16,320/775.5= 21mph@6800rpm.

Now that is @6800rpm 'spec' best power but as you know these engines can spin faster, you put out 7560rpm, just work the math yourself now that you know the math and 'magic number'.

See what just changing that 4G 9T sprocket for the 10T does on paper for example ;-}

The more gear change stages you add in the drive train the tougher it gets to do the math, but it's worth it.
My topic for 4-stroke shifter gearing is here http://kcsbikes.com/topic.asp?TOPIC_ID=942

Hope that helps.