GT5 No torque Low Speed

[FurryOnTheInside]

I will try the solder thing tomorrow. I don't know what tdc is but I assume you mean when the piston head is flush with the cylinder body top. I also don't know what a wrist pin is, so Im guessing you want me to place the solder on the top of the piston head tape it in place, screw back on my cylinder head and crank it over once then remove the head and fetch, and measure the solder.

I used to have a delarto carb but I was unable to adjust the the fuel and it was running too rich so i removed it and bought this rt carb which everyone kept recommending me because "its soo much better than an nt carb". I had an nt carb too and honestly I don't see a huge difference.

Actually I would do it by the second method I posted. The ends of the solder should splay out when they hit the piston dome and the ends find their way to the edge easily enough. The wrist pin is the pivot of the piston. Keeping the solder in line with this means that the piston won't rock over to one side and give you a false measurement.
Don't turn the engine over a full cycle or the solder is scraped all the way down and up the cylinder walls. Start with the piston pretty close to Top Dead Centre, and crank the engine just over Top Dead Centre to squash the solder.
Anyway 125psi (plus an expansion pipe) is plenty to run correctly so it isn't an important issue at the moment.

I had 125psi when I did my compression test on my (new, never been run, rings not seated) engine, and I have no expansion pipe. I have a CNC head, mild porting, and the supposedly crappy NTTC carb, so it's actually a fairly similar engine apart from your pipe.. but I always used an upgraded air filter from the start.
This is, as far as I can see, the most important difference between your engine and mine, and the thing that really needs to be sorted out.
If there is any restriction on the air flow into the carb then your RPM will be restricted. #68 is probably the most popular jet size so its a fine place to start with jetting, but fine tuning your jetting will be pointless if the RED air filter cover is not allowing enough air into the carb.
This is what I use:

NT carb with the filter adapter

• FurryOnTheInside
• Sep 11, 2017

I found this filter adapter on eBay (for scooters) and it fits perfectly. Hopefully this will...

The bolt on adapter allows the use of the 42mm clamp on foam filter.

Huge foam filter

• FurryOnTheInside
• Sep 20, 2017
• 2

Damn, this flows air freely!
I had to trim the outer coarse cover to fit in the frame, or lose...

 

[FNTPuck]

125psi is low for a modern chinagirl. It will run, but won't be high performance. A bone stock triple40 is closer to 140-150psi with a single base gasket. I like to aim for 160-175psi.

The G5 cylinder is a little too tall for the zeda bottom end which causes low compression. Also, what pipe are you running? There is no yz700, do you mean yz80? Thats one of the best pipes we can use.

 

[Sitherus]

125psi is low for a modern chinagirl. It will run, but won't be high performance. A bone stock triple40 is closer to 140-150psi with a single base gasket. I like to aim for 160-175psi.

The G5 cylinder is a little too tall for the zeda bottom end which causes low compression. Also, what pipe are you running? There is no yz700, do you mean yz80? Thats one of the best pipes we can use.

Im sorry its a yz 125

Its been chopped and re-welded to fit my bike.

 

[Sitherus]

Actually I would do it by the second method I posted. The ends of the solder should splay out when they hit the piston dome and the ends find their way to the edge easily enough. The wrist pin is the pivot of the piston. Keeping the solder in line with this means that the piston won't rock over to one side and give you a false measurement.
Don't turn the engine over a full cycle or the solder is scraped all the way down and up the cylinder walls. Start with the piston pretty close to Top Dead Centre, and crank the engine just over Top Dead Centre to squash the solder.
Anyway 125psi (plus an expansion pipe) is plenty to run correctly so it isn't an important issue at the moment.

I had 125psi when I did my compression test on my (new, never been run, rings not seated) engine, and I have no expansion pipe. I have a CNC head, mild porting, and the supposedly crappy NTTC carb, so it's actually a fairly similar engine apart from your pipe.. but I always used an upgraded air filter from the start.
This is, as far as I can see, the most important difference between your engine and mine, and the thing that really needs to be sorted out.
If there is any restriction on the air flow into the carb then your RPM will be restricted. #68 is probably the most popular jet size so its a fine place to start with jetting, but fine tuning your jetting will be pointless if the RED air filter cover is not allowing enough air into the carb.
This is what I use:

NT carb with the filter adapter

• FurryOnTheInside
• Sep 11, 2017

I found this filter adapter on eBay (for scooters) and it fits perfectly. Hopefully this will...

The bolt on adapter allows the use of the 42mm clamp on foam filter.

Huge foam filter

• FurryOnTheInside
• Sep 20, 2017
• 2

Damn, this flows air freely!
I had to trim the outer coarse cover to fit in the frame, or lose...

I looked at both mbrebel and gasbike and couldn't find that adapter. the closest I could find is this https://mbrebel.com/product/air-filter-and-plastic-velocity-stack-for-nt-or-speed-carburetor/
but the metel filters are too restrictive to waste money on.

 

[FurryOnTheInside]

I looked at both mbrebel and gasbike and couldn't find that adapter. the closest I could find is this https://mbrebel.com/product/air-filter-and-plastic-velocity-stack-for-nt-or-speed-carburetor/
but the metel filters are too restrictive to waste money on.

The plastic adapter is like a two dollar thing on ebay for mopeds, minibike or whatever. These are just needed if you want to fit a 42mm clamp on filter to the NT or similar carb that has the two bolts on it for its stock filter housing.
I heard that the cheap folded filters with metal were often restrictive too, which is why I chose the foam type. They are a common thing on ebay too. Usually black or red or black and red. I paid about £5 for the filter and £2 for the plastic adapter. But I don't have access to as many choices as those in the USA.

@FNTPuck
I suppose the squish gap test could reveal something of use, as it tells you whether there is room to cut down the cylinder or change to thinner gasket for more compression, and can help to explain the tested psi, but I think the incredibly low 21mph top speed means that the problem is something extreme, such as perhaps a severe intake restriction.. I tested 125psi and no problem getting to 8000rpm and 40mph without any expansion pipe.
So although yes the modern engines available currently in the USA are often able to make higher cranking pressure it should still, in my mind at least, be able to get to 8000rpm and over 40mph with the expansion pipe, porting and gears. I just recalled reading the RED filter box was mentioned as being an even worse restriction than the black "punisher" filter box on the NT. It's something worth upgrading anyway, so there's nothing really to lose by trying it. (Or by checking the squish gap)

 

[Sitherus]

The plastic adapter is like a two dollar thing on ebay for mopeds, minibike or whatever. These are just needed if you want to fit a 42mm clamp on filter to the NT or similar carb that has the two bolts on it for its stock filter housing.
I heard that the cheap folded filters with metal were often restrictive too, which is why I chose the foam type. They are a common thing on ebay too. Usually black or red or black and red. I paid about £5 for the filter and £2 for the plastic adapter. But I don't have access to as many choices as those in the USA.

@FNTPuck
I suppose the squish gap test could reveal something of use, as it tells you whether there is room to cut down the cylinder or change to thinner gasket for more compression, and can help to explain the tested psi, but I think the incredibly low 21mph top speed means that the problem is something extreme, such as perhaps a severe intake restriction.. I tested 125psi and no problem getting to 8000rpm and 40mph without any expansion pipe.
So although yes the modern engines available currently in the USA are often able to make higher cranking pressure it should still, in my mind at least, be able to get to 8000rpm and over 40mph with the expansion pipe, porting and gears. I just recalled reading the RED filter box was mentioned as being an even worse restriction than the black "punisher" filter box on the NT. It's something worth upgrading anyway, so there's nothing really to lose by trying it. (Or by checking the squish gap)

first off i found out that my carb filter is designed to pull in air from the sides while moving. The air is directed straight into the carb.
https://www.gasbike.net/collections/carburetors-air-filters/products/high-performance-cns-carburetor

I took apart the carb today and cleaned it then removed the cover and just used the foam. I checked the pin and the clip was at the very top. I moved it down one. I took it out and threw a chain. I'll have to fix that tomorrow. I think this minor change has made the engine start easier at least.

I am not going to stick solder into my engine. Im unsure what im doing. I dont want to lose solder in my engine.

 

[Sitherus]

moving the needle clip down only made things worse. I put it back. when it runs out of gas the engine starts to run way better for the last 10 seconds. If the jet I'm running is 68 would going up to 69 be better or down to 67?

 

[FurryOnTheInside]

moving the needle clip down only made things worse. I put it back. when it runs out of gas the engine starts to run way better for the last 10 seconds. If the jet I'm running is 68 would going up to 69 be better or down to 67?

I would check your float height first..

 

[gary55]

moving the needle clip down only made things worse. I put it back. when it runs out of gas the engine starts to run way better for the last 10 seconds. If the jet I'm running is 68 would going up to 69 be better or down to 67?

Try the 67

 

[gary55]

I just noticed you say you have a Jake head. If it is one of the newer "Jake" heads it most likely is so in name only and a copy. Some of the copies had a problem with the landing for the spark plug not being milled deep enough for the electrode to properly enter the chamber. Heads like this ran like s**t but could be fixed with a longer reach plug. If your plug looks like the 1 on the right this plug will probably cure your problems.
NGK, Racing Spark Plug, 14mm, 3/4" Reach, Extended Tip, Cool, Each - Competition Products

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You may also need to go smaller with the jet than 67 because of that sweet assed pipe you're using.

This is what Furry was talking about with the solder. Torque the head on and turn the engine over a few times with the plug out, Then measure the squished ends at the smallest point. Use 1/16" rosin core solder.
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