Zman
Platinum Level Site Supporter
In a previous thread I mentioned I had terrific results with the STIC metering block in my GG big bore 327. I am the main mechanic for our riding group of friends and children ages 17-19. I normally spend a too much time each trip tweaking the carbs for elevation and temperature. So in preparation for our Tennessee spring break trip this year, I installed the STIC metering blocks in four of our other GG bikes (125, 250x2 and a 300). I do not have a local place to ride but from some short test drives around my neighborhood and all four bikes showed improvements across the RPM range. When we got to Wind Rock in Oliver Springs, TN we did an easy first day of testing and tuning. Weather was about 65F/18C. The STIC kits came with 50 pilot jets, 190 Main jet and N3EJ needles.
EC300 2004 - High hour bike with a new piston, new cylinder plating, new reeds and squish set to 0.05"(1.27mm) the bike ran just "ok". It would do a 2nd gear wheelie and you needed to try to wheelie it in 3rd. No matter what we did the bike seemed to have chronic fueling problems, erratic idle and poor fuel mileage even with the NEDG needle. As we were installing the STIC we noticed the stock Keihin needle jet in the metering block was worn on one side so it had an egg-shaped hole. The STIC installation is quick and easy. It totally transformed this 300! It started much easier and idled perfect! It ran smooth at low rpms and in the midrange without all of the burbling and pinging it had before. It SCREAMED through the midrange and revved to new high rpms it never reached previously. The only jetting change we made was to richen the needle to address a transitional lean spot. The fuel mileage just about doubled. This was the single best and easiest change we ever made to this bike! The bike now easily wheelies in 4th gear and you can coax it up in 5th occasionally. It was bittersweet when my 19yr old godson wheelied off his brand new rear fender.
MC250 2004 ? This bike was fresh and ran great before the STIC so I was not sure what to expect because it honestly always ran so well. It started and idled well and ran like a nice strong 250. It was a lot of fun to ride. I was surprised to find that the STIC made it noticeably better across the board. It started even easier, idled great, ran cleaner throughout the power band and it revved to a noticeably higher rpm than ever before. I needed to tweak the jetting twice and ultimately ran the N3EJ needle in the richest clip setting to address a minor transitional lean spot. It feels very snappy for a 250 and it wheelies pretty easily in 4th which is a gear higher than before the STIC.
EC250 1998- I think this bike was somehow purchased and not ridden by the previous owners. It has very few miles on it so it is a very young 21yr old bike. �� I jetted it with a CCK needle 45 pilot and 178 main jet. It ran well but was not as dialed in as the MC250. Similar to the MC250, after the STIC installation, it needed the needle to be set all the way rich to address a lean transition but after that it starts, idles and runs fantastic across the rpm range and in all of conditions we rode in. The older GG 1998 GG bikes have a smaller fuel tanks and this bike sips fuel now!
Fuel Range- We have been running these trails for the last 8 years and we all noticed a big change in fuel range for the 250s, 300 and my 327. It is easily 20% higher than before the STIC. The 125 lost about 20% range but I know that is because we had to richen it up so much to fix the off idle bog.
Transitional fueling- after riding behind each of these bikes I noticed something very interesting and very different from the bikes previously. All of the bikes gave a small cloud of exhaust smoke under higher load conditions or during heavier acceleration conditions like going up steep hills. George Boswell, designer of the STIC, told me that the STIC is able to sense the change in engine load and compensates with a richer mixture. This acts like an accelerator pump function and made a huge difference as it would allow you to have a leaner light load jetting while still having a proper mixture under higher load conditions.
MC125 2001- This bike has been a big challenge since we purchased it. I thought it would be similar to our 2003 EC125 that had good low end and was easy to ride. Wow were we wrong! To make matters worse my 17yr old god-daughter rides the MC125 it like a 4 stroke trail bike. Despite countless hours of tuning it has been a problem since day one. The EC and MC have very different characteristics which are probably related to the porting and Messico pipe. The MC125 screams like a 125 mx bike should, but it not happy during transitional fueling at low rpms. It often bogs and dies at the base of hills. I rebuilt the engine top to bottom, cut the head to 0.04? (1mm) squish, increased the compression a lot (150psi to 200psi). To help compensate for the Messico pipe, I made a 3/8? 10mm spacer to extend the head pipe length. Prior to the STIC we had a PWK 35mm from an early KX125 and it ran better than the stock 38mm but it was still not as good as our EC125.
I mentioned our MC125 challenges to George Boswell and he told me he was having great luck with the STIC in 38mm PWKs on the 125 MX bikes so we tried one on the MC125. While it started more easily, idled cleaner and RIPS through the midrange and top end better than with the 35mm PWK, we had to do more work to fix the off idle / low rpm lean bog. Ultimately we richened the main jet to a 192 and richened the needle all the way. While this fixed the bog down low, the bike is running rich in other areas now and the fuel range dropped. I am confident I can fix this with a different needle with a smaller diameter off idle section but we did not have one with us during the trip.
Needle Jet Wear - After some research I learned that the needle jet (the carb portion the needle rides in side of/touches when it goes up and down) wears larger and oval over time and that creates carburation problems as described in the below link. The extra wear in the needle jet reduces the vacuum signal to pull fuel and makes it difficult to properly jet the bike. https://thumpertalk.com/forums/topic/1197062-pwk-38-worn-needle-jet/ FYI- Unfortunately that stock Keihin needle jet is not a replaceable item on that Keihin carb.
Summary- The STIC seems to do have several big benefits over the stock Keihin metering block. It seems to have a stronger fuel draw / signal and responds quickly to engine load changes. It richens automatically during increases in engine load so it does a better job of transitional fueling. It seems to do a better job of fuel atomization and runs much cleaner over the rpm range. It made a big difference in fuel range. The increase in overall power on all 4 bikes was noticeable and significant, but the biggest benefit was the better ridability and throttle response throughout the power band. I know this is going to sound like an advertisement, but honestly it has been the best mod I have found for the money and it is an easy installation.
I have to sort out the 125 and have some good ideas so if all goes well it will not take too long. I need to do some fine tuning on the 250s and 300 because I would like some ability to adjust the needle richer in cold weather. I may try the NEDG Suzuki needle like I am running in my GG 327. I have been talking with George Boswell (+1-715-479-7822) designer of the STIC and he is very knowledgeable and was super helpful in getting me the correct STIC version for our different bikes. George told me they are having good luck with larger main jets to address transitional fueling issues so that is another option to try.
EC300 2004 - High hour bike with a new piston, new cylinder plating, new reeds and squish set to 0.05"(1.27mm) the bike ran just "ok". It would do a 2nd gear wheelie and you needed to try to wheelie it in 3rd. No matter what we did the bike seemed to have chronic fueling problems, erratic idle and poor fuel mileage even with the NEDG needle. As we were installing the STIC we noticed the stock Keihin needle jet in the metering block was worn on one side so it had an egg-shaped hole. The STIC installation is quick and easy. It totally transformed this 300! It started much easier and idled perfect! It ran smooth at low rpms and in the midrange without all of the burbling and pinging it had before. It SCREAMED through the midrange and revved to new high rpms it never reached previously. The only jetting change we made was to richen the needle to address a transitional lean spot. The fuel mileage just about doubled. This was the single best and easiest change we ever made to this bike! The bike now easily wheelies in 4th gear and you can coax it up in 5th occasionally. It was bittersweet when my 19yr old godson wheelied off his brand new rear fender.
MC250 2004 ? This bike was fresh and ran great before the STIC so I was not sure what to expect because it honestly always ran so well. It started and idled well and ran like a nice strong 250. It was a lot of fun to ride. I was surprised to find that the STIC made it noticeably better across the board. It started even easier, idled great, ran cleaner throughout the power band and it revved to a noticeably higher rpm than ever before. I needed to tweak the jetting twice and ultimately ran the N3EJ needle in the richest clip setting to address a minor transitional lean spot. It feels very snappy for a 250 and it wheelies pretty easily in 4th which is a gear higher than before the STIC.
EC250 1998- I think this bike was somehow purchased and not ridden by the previous owners. It has very few miles on it so it is a very young 21yr old bike. �� I jetted it with a CCK needle 45 pilot and 178 main jet. It ran well but was not as dialed in as the MC250. Similar to the MC250, after the STIC installation, it needed the needle to be set all the way rich to address a lean transition but after that it starts, idles and runs fantastic across the rpm range and in all of conditions we rode in. The older GG 1998 GG bikes have a smaller fuel tanks and this bike sips fuel now!
Fuel Range- We have been running these trails for the last 8 years and we all noticed a big change in fuel range for the 250s, 300 and my 327. It is easily 20% higher than before the STIC. The 125 lost about 20% range but I know that is because we had to richen it up so much to fix the off idle bog.
Transitional fueling- after riding behind each of these bikes I noticed something very interesting and very different from the bikes previously. All of the bikes gave a small cloud of exhaust smoke under higher load conditions or during heavier acceleration conditions like going up steep hills. George Boswell, designer of the STIC, told me that the STIC is able to sense the change in engine load and compensates with a richer mixture. This acts like an accelerator pump function and made a huge difference as it would allow you to have a leaner light load jetting while still having a proper mixture under higher load conditions.
MC125 2001- This bike has been a big challenge since we purchased it. I thought it would be similar to our 2003 EC125 that had good low end and was easy to ride. Wow were we wrong! To make matters worse my 17yr old god-daughter rides the MC125 it like a 4 stroke trail bike. Despite countless hours of tuning it has been a problem since day one. The EC and MC have very different characteristics which are probably related to the porting and Messico pipe. The MC125 screams like a 125 mx bike should, but it not happy during transitional fueling at low rpms. It often bogs and dies at the base of hills. I rebuilt the engine top to bottom, cut the head to 0.04? (1mm) squish, increased the compression a lot (150psi to 200psi). To help compensate for the Messico pipe, I made a 3/8? 10mm spacer to extend the head pipe length. Prior to the STIC we had a PWK 35mm from an early KX125 and it ran better than the stock 38mm but it was still not as good as our EC125.
I mentioned our MC125 challenges to George Boswell and he told me he was having great luck with the STIC in 38mm PWKs on the 125 MX bikes so we tried one on the MC125. While it started more easily, idled cleaner and RIPS through the midrange and top end better than with the 35mm PWK, we had to do more work to fix the off idle / low rpm lean bog. Ultimately we richened the main jet to a 192 and richened the needle all the way. While this fixed the bog down low, the bike is running rich in other areas now and the fuel range dropped. I am confident I can fix this with a different needle with a smaller diameter off idle section but we did not have one with us during the trip.
Needle Jet Wear - After some research I learned that the needle jet (the carb portion the needle rides in side of/touches when it goes up and down) wears larger and oval over time and that creates carburation problems as described in the below link. The extra wear in the needle jet reduces the vacuum signal to pull fuel and makes it difficult to properly jet the bike. https://thumpertalk.com/forums/topic/1197062-pwk-38-worn-needle-jet/ FYI- Unfortunately that stock Keihin needle jet is not a replaceable item on that Keihin carb.
Summary- The STIC seems to do have several big benefits over the stock Keihin metering block. It seems to have a stronger fuel draw / signal and responds quickly to engine load changes. It richens automatically during increases in engine load so it does a better job of transitional fueling. It seems to do a better job of fuel atomization and runs much cleaner over the rpm range. It made a big difference in fuel range. The increase in overall power on all 4 bikes was noticeable and significant, but the biggest benefit was the better ridability and throttle response throughout the power band. I know this is going to sound like an advertisement, but honestly it has been the best mod I have found for the money and it is an easy installation.
I have to sort out the 125 and have some good ideas so if all goes well it will not take too long. I need to do some fine tuning on the 250s and 300 because I would like some ability to adjust the needle richer in cold weather. I may try the NEDG Suzuki needle like I am running in my GG 327. I have been talking with George Boswell (+1-715-479-7822) designer of the STIC and he is very knowledgeable and was super helpful in getting me the correct STIC version for our different bikes. George told me they are having good luck with larger main jets to address transitional fueling issues so that is another option to try.
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(NZ dollars) however I bought a very cheap 17 carb to replace my worn out 07. I am so happy with the RM needle.