GX160 easy mods

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Wolfie

New member
Hi I would appreciate some advice please.

I am in the UK and have a cadet kart for my son, he does not race as we are just getting him seat time at the moment, he may or may not race in the future.

I have a couple of GX160's that i would like to get a little more power out of, the engines are MSUK SP spec and have billet conrods. So far i have taken out the carb restrictor plate but is there anything else i can do? Timing? setup? different spark plug? The value in the engines is that they are to MSUK spec so i don't want to be changing cams or skimming heads right down i need to be able to put the engines back to MSUK spec easily if he does not want to continue or wants to race.

Many Thanks
 
I'm also in the UK.
A friend of mine used to run his son in Prokart racing, The engines were RPM sealed, they used to use gx140 springs, adjust the timing with Flywheel advance keys and finally jet the carb accordingly. The colour of the plug would aid in sizing up the jet. You are looking for around 32-34 btdc on the timing, GX tuning parts will be able to advise, they've probably got the correct offset key on the shelf. A stripped out exhaust will also give you a little more.
Unfortunately all the work is in the porting of the head, changing the carb and a high flow exhaust.

Might be worth looking at it another way, sell the engines and buy two JCB 224 for £159 each, remove the governors and you have around 8hp per engine.
I'm building a 27hp JCB at the moment.
Now I'm going to bore you.....
America have a massive gx style clone industry, Harbor Freight sell the Predator 225 clone engine produced by DUCAR in China, this is the biggest bang for buck engine using the GX 160/200 platform. We have been waiting for the DUCAR engine to come to the UK and now GENPOWER import it for JCB,
The predator engine is used in America for MINI Bikes and all sorts of Go Karts, they produce a Predator called a Ghost, this is specifically built for the go kart market, the DUCAR engine has proved itself to be one of the best clones out there, just type Predator 224 on youtube and you'll understand why it's so popular.
I have a build diary on Diy Karts, I go through the jcb engine.

https://www.diygokarts.com/communit...uild-with-full-efi-control-gx200-clone.48159/
hope this helps
D
 
Also if you took the plate off the carb you will probably need to rejet the carb for best performance. But if you are wanting to be able to switch back to the spec engine, I would just buy a bigger carb and jet it accordingly to the engine. Then when you are done with your seat time, pull the bigger carb and switch it back to the smaller carb with plate.
 
Do you have to run the stock airbox/intake? That's a pretty big choke point if you do. Change to an external filter and re-jet as needed. Exhaust is the same, stock is pretty restrictive even after the baffle is removed, assuming this is something you have to run.

You could lap the flywheel and add a little ignition advance. Valve springs are quick and easy to change, I remember GX120 (or 140?) springs in the GX160 was a popular change in the prokart class (might still be?). Partially covering the recoil and/or removing fins from the fan can give a boost, but you'll have to be careful to not overheat the engine of course. That's an easy thing to swap between stock and "modded".

Re on bigger carbs I'm not sure what fits the stud spacing on the smaller blocks, if you wanted to go to say a 21mm from a GX390 there are adapters available to run them with the small block spacing.

If you're open to removing the head you could go with a thinner head gasket to bring the compression up a little without having to do any machining.

Spark plug won't give you any gains. Stick with the NGK 6 range. Like anything, depends how deep down the rabbit hole you want to go.
 
He wants to keep the engines sealed and carry out external 'easy' mods that can be as easily changed back. I'm guessing he's not an engine guy because of the questions he asked.
 
Thanks all. The engines are not sealed but could be sealed for a small charge, that's why i was just looking at small reversable mods. I will get a gx200 carb fitted to one of the engines and get it tuned and see if there is any benefit. Is there smll gains to be had from changing the woodruff key from standard to say 2 or 4 degrees? I am mechanically minded but have never worked on these little engines before.
 
Plenty of places will do an offset key set, this will allow you to play, but you need to determine where you are now as the engines stand. The aim is 32 btdc, If the revs rise, more chance of a valve bounce/float, a bigger carb will let the engine breathe better and rev higher again more chance of valve float.
If these are true kart engines, they should have 10lb springs in them, and the timing should have already been altered for higher revving. So carb and exhaust are the next stage.
Didn't mean any disrespect on the above comment, I was pointing out that this type of engine is not known to you.
Since they are not sealed then a thinner head gasket will also help by raising the compression ratio, these may already have a thin head gasket if built as a performance engine

https://www.ebay.co.uk/itm/26668563...g7+yOAt8E5VdFgNvO92shVYA==|tkp:Bk9SR8aSnqC_Yw
 
Wolfie said:
I will get a gx200 carb fitted to one of the engines
Click to expand...
Is the gx200 carb larger? I was under the impression it’s the same as the 160. I think you have to go to the 240 before you see a Venturi size change, but it’s also a different stud pattern.
 
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