GT5 No torque Low Speed

Sitherus

Active Member
Joined
Apr 4, 2016
Messages
252
My engine is a GT5 Stinger with a Jakes head and a ported cylinder body. I'm running a yz700 exhaust and a boost bottle. I also have an rt carburetor and an SBP shift kit, with an HD freewheel.
My Bike frame is a Felt Vintage Iron Bolt, with a sealed gas tank. Im using the recommended NGK spark plug, and running 20-1 ethanol free premium.

Previously I came on here to troubleshoot this same issue and there was an almost unanimous agreement that is was my gearing. so I upgraded to a Shimano TZ31 7-Speed 14-43t Freewheel, next I checked for air leaks and discovered one on my intake so i added an o-ring which fixed it. I re-checked and found no additional leaks.

I was wondering if replacing the magnet and getting a keyed more powerful CDI would help things?

I took it out today and was able to make 21 MPH on flat land.

Am I wrong in thinking this should be much faster?
I just built a completely stock kit for my friend and he is faster than me by allot.
 

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Jag

Active Member
Joined
Oct 6, 2018
Messages
199
My engine is a GT5 Stinger with a Jakes head and a ported cylinder body. I'm running a yz700 exhaust and a boost bottle. I also have an rt carburetor and an SBP shift kit, with an HD freewheel.
My Bike frame is a Felt Vintage Iron Bolt, with a sealed gas tank. Im using the recommended NGK spark plug, and running 20-1 ethanol free premium.

Previously I came on here to troubleshoot this same issue and there was an almost unanimous agreement that is was my gearing. so I upgraded to a Shimano TZ31 7-Speed 14-43t Freewheel, next I checked for air leaks and discovered one on my intake so i added an o-ring which fixed it. I re-checked and found no additional leaks.

I was wondering if replacing the magnet and getting a keyed more powerful CDI would help things?

I took it out today and was able to make 21 MPH on flat land.

Am I wrong in thinking this should be much faster?
I just built a completely stock kit for my friend and he is faster than me by allot.
Try 32:1 klotz supertechni plate
And make sure air filter is clean and bike is jetted properly
 

The_Aleman

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Joined
May 2, 2007
Messages
1,046
Sounds like you're jetted wrong. A chinagirl running too rich will just 4-stroke itself into mediocrity. Sure, it'll get by, but if you expect it to actually accelerate without using your chevrolegs, it's gotta be jetted right. Before even figuring out if you got the right jet, you gotta make sure you have no air leaks whatsover.

You say you're running a boost bottle. Well, I ran a home-made one tailored for my engine displacement for over a year on a HT of mine, and I gotta say - your engine needs to be tuned well in the first place before you can even begin to make use of what little it has to offer. My opnion is that it's not worth it, it's mostly a gimmic. At best, you'll see a slight bump in midrange, at worst your engine is going to lack tuning at a certain RPM, because that's the nature of the beast. That might be an RPM you don't care about, but with these things, chances are that it'll be a hindrance.
 

Sitherus

Active Member
Joined
Apr 4, 2016
Messages
252
Sounds like you're jetted wrong. A chinagirl running too rich will just 4-stroke itself into mediocrity. Sure, it'll get by, but if you expect it to actually accelerate without using your chevrolegs, it's gotta be jetted right. Before even figuring out if you got the right jet, you gotta make sure you have no air leaks whatsover.

You say you're running a boost bottle. Well, I ran a home-made one tailored for my engine displacement for over a year on a HT of mine, and I gotta say - your engine needs to be tuned well in the first place before you can even begin to make use of what little it has to offer. My opnion is that it's not worth it, it's mostly a gimmic. At best, you'll see a slight bump in midrange, at worst your engine is going to lack tuning at a certain RPM, because that's the nature of the beast. That might be an RPM you don't care about, but with these things, chances are that it'll be a hindrance.
Try 32:1 klotz supertechni plate
And make sure air filter is clean and bike is jetted properly
I am using a #68 jet based on a recommendation. I have others, I found 65-69. Im not sure if i have more.
 

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FurryOnTheInside

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Joined
Sep 23, 2013
Messages
3,685
I seem to recall reading that the red air filter cover is even more restrictive than the black one that comes with the stock NT or NTTC carb. (I have not tried either of them, I just upgraded from the start.)

BTW have you done a compression test? What is the cranking pressure? And the squish gap?
 

Sitherus

Active Member
Joined
Apr 4, 2016
Messages
252
I seem to recall reading that the red air filter cover is even more restrictive than the black one that comes with the stock NT or NTTC carb. (I have not tried either of them, I just upgraded from the start.)

BTW have you done a compression test? What is the cranking pressure? And the squish gap?
I have 124 psi, also I didn't know what a squish gap was until i just looked it up. I am unsure how to measure that.
 

FurryOnTheInside

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Joined
Sep 23, 2013
Messages
3,685
I have 124 psi, also I didn't know what a squish gap was until i just looked it up. I am unsure how to measure that.
That's plenty of cranking pressure. If the pipe does its job then it will add to that too.
Knowing the squish gap allows you to explain the situation with the cranking pressure and whether you have room to increase it.
If you remove the head you can tape some solder across the piston (in line with the wrist pin), while the piston is near TDC, and then put the head back on and crank the engine over TDC to squash the solder, remove the head to retrieve the solder and measure the thickness of the squashed ends with a vernier caliper.
You may also be able to bend a decent length of solder into a 人 and insert the two ends carefully through the spark plug hole, while the piston is close to TDC, to splay out and reach the edges of the bore, in line with the wrist pin, then crank the engine over TDC and pull it back out. This is what I did the last time, so I wouldn't have to keep replacing my twisted Teflon tape gasket.

I think I would be more concerned about the red air filter cover, if that is what I am seeing in the photo. It will restrict airflow and therefore RPM.
 
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Sitherus

Active Member
Joined
Apr 4, 2016
Messages
252
That's plenty of cranking pressure. If the pipe does its job then it will add to that too.
Knowing the squish gap allows you to explain the situation with the cranking pressure and whether you have room to increase it.
If you remove the head you can tape some solder across the piston (in line with the wrist pin), while the piston is near TDC, and then put the head back on and crank the engine over TDC to squash the solder, remove the head to retrieve the solder and measure the thickness of the squashed ends with a vernier caliper.
You may also be able to bend a decent length of solder into a 人 and insert the two ends carefully through the spark plug hole, while the piston is close to TDC, to splay out and reach the edges of the bore, in line with the wrist pin, then crank the engine over TDC and pull it back out. This is what I did the last time, so I wouldn't have to keep replacing my twisted Teflon tape gasket.

I think I would be more concerned about the red air filter cover, if that is what I am seeing in the photo. It will restrict airflow and therefore RPM.
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.
 
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