49cc exhaust and other mods

[Frankenstein]

I swapped spark plugs with the NGK ive seen recommended on these boards, and i changed the oil to 10w30. (I had started with SAE30) I just took it out and got it up to 26 mph! Still seems kinda weak.. The Q matic pacesetter transmission i ordered should be arriving soon, so ill see what that does before i continue on with modifications.. I read that an aftermarket exhaust can increase HP by up to 18%? can anyone recommend a good one? or a place to get the parts to make one? I have no problem doing some cutting and welding, i also have no problem just shelling out the money for a premade one lol. I just cant seem to find one in stock anywhere, or the 7/8" ID exhaust pipe anywhere either..

18% increase in power? This is only true if the pipe they initially tested on was half blocked by a crap weld job and they were too stupid to realize it, or they are full of s**t and hoping that you are too stupid to realize it.

A 4 stroke will not benefit after a fine line is crossed when it comes to a pipe, once it's large enough to not be of any real restriction (like the size of the exhaust port and larger) that line is crossed. A 2 stroke is a completely different story because they operate in a different way when it comes to exhaust (like right now there's a leak in my exhaust about 4 inches from the exhaust flange, it's detectable by the semi lean way it makes the motor run especially if starting fluid or brake cleaner is sprayed on it at that spot, it acts just like a small leak on the intake would since a 2 stroke scavenges what's leaving in the exhaust pipe. A similar leak on a 4 stroke wouldn't even be noticed unless you looked for the muck, certainly wouldn't change how it ran)

18% is too large a claim to be respectable, whoever wrote that is on drugs or lying to people, so as long as they are claiming this in a 4 stroke that is, I suggest not following their example.

As mentioned before there's not all that much that can be done to better the power of a 4 stroke unless you are looking to make serious modifications, and even then you won't get more from a 49 than you will a 79 regardless of the modification, so with that if you are going to go all out balls to the wall it may just be plainly cheaper and easier to get a slightly larger motor and install that, and no doubt the power behind that will satisfy whatever it is you are yearning for in the 49.

79cc can be found for what a hundred dollars? Harbor freight sells them often at that price and even have coupons or whatever for it, and the bolt pattern on the mounts are the same and the q-matic uses the same bolt pattern for all 3 size 4 strokes that you'll commonly see in a bicycle. I think even the drive shaft is the same diameter so no worries even in that.

I've never had mine flat out yet but it will do 38 without a problem. I know it will go faster. At 25 you hit the gas and it pulls hard! All stock but I run premium fuel and I too the stock pipe apart and drilled it out a little bigger for free flow. There is a company I found that made hi lift cams, but he said they had no plans on grinding more at this time. I'm trying to find a way to talk them into a run of them. I know I could get rid of them if I could get them a decent price. I will post if I can make a deal with them.

Does 93 octane actually make a difference on that small 49 4 stroke? I don't know do they have that high of compression or get that hot?

 

[To cool for school]

It probably dose not make any difference. It's all I've run in it. On yours, if yo have stock gearing. My thought is your carb is probably junk. These things have junk for carbs. Can you tell if your clutch fully locks up or is it slipping all the time? Just took mine for a Cruze. My gearing is only 2 teeth bigger on the rear sprocket. So not much over stock and at 22mph, if I let off the gas and then come back on just enough to maintain speed. I'm not too much over an idle. No where near wound out. So if your only getting to mid 20s with stock gears and it's sound wound out. Your clutch is slipping bad. If I'm cruzzing along and snap the throttle, I feel the a thud as the power hits because the clutch is locked 1 to 1 and not slipping. (I also don't use the rag joint,) my sprocket it bolted to my hub so when the power comes on it hits hard. There's no flex of the rag joint or spokes.

 

[Jakeguy24]

it doesnt sound wound out at all. it sounds very governed and steady, like a lawn mower. i do not think the clutch is slipping when it does get up to that speed

Thanks for the input on the 79cc. At this point, it seems all i would need to do is to buy the engine, so thats pretty manageable lol.

 

[To cool for school]

That's not true! I'm not the one that suggested the 79cc! You can go that route, but none of your stuff will bolt up to that motor! It's a whole different kit! There big HP and cool. But you can't just get the motor and bolt in place of yours! If you can blow through your muffler and there's no restriction. Replace the carb. You can get one for $35.

 

[CrazyDan]

The qmatic drive will bolt up to 49cc, 79cc and the 99cc straight shaft engines.

 

[KCvale]

I swapped spark plugs with the NGK ive seen recommended on these boards,
and i changed the oil to 10w30.
I just took it out and got it up to 26 mph!
Still seems kinda weak..

I read that an aftermarket exhaust can increase HP by up to 18%? can anyone recommend a good one?

I don't think an 18% power increase, but yes, the first thing you want to do with an HS 142 is pull that stock box exhaust off and with a couple other simple mods I can 'feel' ~18% in overall improvement, though it is more pronounced on the 142F's big brother, the 144F 53cc.

I just put on a $15 gasbike 2-stroke pipe, it has no catalyst in it so it flows very free.
https://www.gasbike.net/collections/mufflers/products/chrome-exhaust-muffler-1

You have 2 choices when it comes to a better air cleaner, and it can be performance changer...
I'm a 'green' kind of guy so I use the SBP big chrome air filter with a PVC intake for the engine crankcase gases.

http://sickbikeparts.com/4-stroke-air-filter/

The thing is, those crank case gases actually hamper performance.
Granted it's by not much, especially with a big air filter and a good new engine, but it's a little.

You can't just close off the hole, the crank case needs to vent.
You can't just leave the hose off either as it will let water in and make a constant mess of your bike from the oily blow by.

What you can do is just put a 'Catch Can' on your bike and run the vent line to it.
I don't dick with that though, it's just one more thing that needs maintenance for a minimal gain, I just mention it because it is an option.

 

[Jakeguy24]

That's not true! I'm not the one that suggested the 79cc! You can go that route, but none of your stuff will bolt up to that motor! It's a whole different kit! There big HP and cool. But you can't just get the motor and bolt in place of yours! If you can blow through your muffler and there's no restriction. Replace the carb. You can get one for $35.

lol, i was responding to 2 different people with my 2 different lines there.. I checked the muffler per your suggestion, and it looks like replacing the carb is next on my list.. do you guys recommened the stock 4 stroke replacement, or would there be any benefit from putting a regular NT carb on like ive read about people doing?

 

[KCvale]

it looks like replacing the carb is next on my list.. do you guys recommened the stock 4 stroke replacement, or would there be any benefit from putting a regular NT carb on like ive read about people doing?

The stock carb works just dandy when you let breath.
You can stick an NT on it, but it's smaller.

 

[gary55]

The stock carb on 49cc 4 stroke is 10.8mm, NT carb is 14mm. The NT is not smaller and can be made to run better than stock, but is a pain in the ass to get jetted right. Check with affordablegokarts. If you send them a stock carb. they will bore and rework it for better performance. Pricey but professional and experienced.

 

[Jakeguy24]

i took the carb off and took it apart. in the bottom of the bowl were metal chips. not shavings, actual big chips. Wish i would have taken a pic.. i blew everything out good with compressed air and thoroughly sprayed it with carb cleaner. Ill try it again in a couple days, before i order a new carburetor. Just wondering tho, what exactly would make one of these carbs "bad" and make the RPMs act governed and steady like mine?