GX200 Clone Jetting

[Brad_R]

Hey guys, long time no see?

Anyway, got a new engine, picked it up from a second hand shop for £40. It's a GX200 clone and it runs. I havn't done much to it apart from change the plug (To a BPR6ES), change the oil to RockOil 4 Stroke Oil (I think its SAE 30, got it for £3 so it will do for now!) and give a minor clean.

I was thinking about making a minibike and using it, but using it on my soon-to-be-scrap-metal gokart for the last time (It's far too small for me now, I'm 16 and it was built when I was turning 14)

The problem is, It needs around 1 minute to warm up before it will accept any revs without dying. It will not start without half or full choke - which is understandable - and can be instantly switched to no choke when it's started. I am in need of some information on how to fine-tune the mixture as I cannot find information on this. (This is my first serious working Honda, check my previous posts to find out the problems with my GX340, if you want )

Here's what I am thinking:
Changing the emulsion tube to a GX140 E-Tube and rejetting if its needed. However, I have no idea about the jetting or emulsion tubes. I had to ask GranPann on Youtube (Forgot his DIYGK username, thanks anyway though!).

Heres where I'm stumbling a bit. I would have no idea of knowing what sized jet to use and even what effect it would have to the engine. I gathered it will make it run richer.

I'm hoping you smart people of the forum could help

Cheers,
Brad

 

[Russ2251]

It is not a question of it's worth, but what works for you.
No two engines are alike. A very few need jetting, most do not.

 

[Brad_R]

I understand your point but Im not sure of the ins and outs of jetting. Hence why posting here

 

[firemanjim]

The jet let's in fuel during acceleration. The bigger the jet, the more fuel is going to flow.
The emulsion tube breaks the fuel down to smaller particles (basic explanation ) so it can mix with the incoming air more efficiently. If the emulsion tube is bigger, then more fuel will flow.....
Opening up the idle jet a little, helps the engine go from idle to part throttle/full throttle by letting in more fuel as it transitions between the 2 jets....
IDK.......
If you still have the governor, there's no real point in doing these mods. These mods really help PAST 3600 rpms, the set governed max.... Just get the right gear ratio for you and your bikes weight.

 

[Brad_R]

Thanks for that.

If I removed the governor (Never done it before), and made these mods, what sort of differences would I get compared to a stock GX200 (Clone)?

I was also thinking about a racing air filter, with the correct adapter and a homemade straight pipe without a silencer/muffler. Combined with the governor removed, jetted and with an E-tube, what sort of difference would I get?

Cheers

EDIT: I have ordered a Hour/Tach to be able to tune and observe the engine in further detail.

 

[OzFab]

No matter what engine we're discussing, every engine acts differently from cold to operating temp; what works once the engine has warmed up won't work the same as when it's cold...

If you start playing with the fuel delivery to work better when the engine is cold, you start messing with how it will work at operating temp, more often than not, detrimentally...

The simple fact is this: You can't expect any engine to run properly when it's cold, every engine needs a "warm up" period; deal with it...

 

[Brad_R]

I understand how they act differently when cold, but I am also asking how to adjust the mixture on these machines as I know for a fact the mixture is off.

 

[firemanjim]

How do you know the mixture is off?
All my Hondas,and Honda clones, are started with the choke on. Then after 30 seconds, I open the choke,sometimes sooner, depends on what the engine is saying. After I open the choke, it sits for another minute or so while we get ready to go tear some... Errr.... Go ride.
They ALL need that minute of warm up time. There is no way around it. It's a mechanical thing......
There is no air mix screw..... You have a screw for the idle circuit and the idle adjustment screw.
As a warning, when you do all the mods, your warm up time might be a hair longer..... And speaking of the mods...... High flow air filter, straight pipe,and no governor, will add up to about a 3-4hp increase. Further tweaking can produce a 7-12hp..... Depends on how much bread you want to drop.....

 

[Scout]

If you are still running the stock air filter and exhaust, then changing the jets won't help much.

Pull the spark plug out and post a picture of the electrode. If it's shiny like a glazed doughnut then it's running lean and hot. If it's black and sooty it's running rich. If it's tan, then it's pretty good so don't mess with it.

 

[Brad_R]

It's a brand new plug so il run it for half hour and send a picture.

What are some cheap mods to do? I'm 16 so not much money available but I'm willing to spend 5 or 10 pounds here and there.

Do you know anywhere to get these high flow filters in the UK? I'm sure I could make a straight pipe with my grandad. These mods wouldn't need new uprated parts would they?
By '' further tweaking'' do you mean flat top piston, longer spark plug, milled head, new springs etc etc?

 

[OzFab]

There's a list of mods a mile long (that's not an exaggeration), everything from hotter spark plugs to billet conrods; it all depends on how much you want to spend...

On a micro budget, we can show you some easy tweaks to gain a little HP but, nothing overly substantial, I'm afraid...

 

[Brad_R]

Oh OK, I guess with a bit of saving I could squeeze some more juice out of the clone. Would you mind telling me some 'micro mods' please?

 

[fowler]

pod filter
Straight though exhaust
Governor removal
Rejet

U have sort of covered most of the mods already

If your game u can try some porting
Or head gasket elimination

Or some of the less agreed apon mods like removing every second cooling fin on the flywheel

Out of the above list I wouldn't have to leave home or spend money on a single of the above mods

It all depends how much access to tools u have and your skills using them

I got carried away the other day on my lawn mower
Started my tryi g to find an air filter
Cant
So made one out of a sticking (high flow)
Then took a tiny dril bit to the jet to get it to run right

Then it ran way better than ever before
So I took it apart again and ported it with a die grinder and flapper disc just to see whst would happen
Got a little more responsive

Then decided to stop before it gets a straight pipe and my neighbors hate me
Also painted it and sharpenes the blades

 

[Brad_R]

Thanks, that's a great list!
How does removing the head gasket work? How much extra power would it gain? Also what sized jet could I use for a bit more power with the stock intake? I don't have enough money to buy the high flow filter and adapter and import it to the UK.
I don't think my neighbours will like me for much longer either.

 

[Half-breeder]

Just remember that some mods need 'other' items before they 'should' be installed. we will tell you the order if you post questions.

 

[Brad_R]

Ok thats understandable, so what would I need to get before jetting and getting a 140 etube, along with a straight pipe and governor removal?

 

[Half-breeder]

High flow intake... after that... then u jet/header(actually all at once is better). Run for a few mins at normal use... pull plug n check if youer runnin rich, lean or between (lil rich is better than alil lean). IMO while you got the case open, id replace the conrod/pin n shaft bearings/seals... but that's just me.
highflow intake w/ filter~25$
Conrod w/ pin~10$
Bearing/seals~15$
+shipping

Plus you're gonna need a gasket set if you're removing the governor. Id never reuse gaskets when upgrading/altering from factory specs.

 

[Brad_R]

Ok, thanks for that.
Should the conrod be genuine or can it be clone?
Also I'm in the UK so the filters and adapters are a pain in the butt to get hold of, do you know anywhere with low international postage costs?

Finally, would you/are you allowed to post links to these parts?

EDIT: I think il replace the piston to a flat top one depending on price if I change the rod

 

[Brad_R]

That's what I have at the moment, size 72 jet is quite common on eBay so I guess it's a good size?

 

[Half-breeder]

Ok, thanks for that.
Should the conrod be genuine or can it be clone?

Honda for a Honda is the best bet(clones 'tend' to have different cc's). 'IF; you can afford it... a 'billit' conrod is what you want(but probably wont wanna buy)... but a factory replacement is good if you dont take the engine over 5k rpms(which is done by replacing the springs... but I HIGHLYdo notrecommend that, unless you're wanting to possibly have to rebuild the engine every 20-40hrs of use)

Finally, would you/are you allowed to post links to these parts?

Sure you can... not guaranteeing anyonell click on them... around here pics n vids are a 'seller'... links tend to turn ppl away...

EDIT: I think il replace the piston to a flat top one depending on price if I change the rod

I did that to mine aswell as bore +.020(had rust holes eaten away inside the cylinder). EVERYONE ive talked to says it was a good investment. If you get a new piston, youll want to get new rings aswell, mainly for insurance reasoning(no sense in possibly having to replace something later, when you can/should do it now and pretty much have a 'new-ish' engine. The cylinder 'should' be honed before you put everything together. Most any machine shop(and some mechanics) will be able to accommodate the honing for a few dollars. Honing the cylinder smooths out any rough area's/sections, causing less drag on the new rings, allowing them to seat properly... sooner. If the rings dont seat w/ the cylinder walls(fully) then compression tends to slip past the rings, which means you are throwing away HP.