Thank you! i thought it would be fun to show the process and failures that can occur while trying to upgrade performance without the use of a dyno or other expensive diagnostic tools. Tearing the bike apart and then rebuilding is part of the fun! This is the first time I have tried to do something like a big bore kit for a fuel injected cycle. I have some successful experience with two-strokes using carburetors. There it was simply changing jets.
LOL! You would definitely need some grease for that (the egg)! Realistically, the grease will wash away in the first few cranks of the cylinder. Oil is a better choice but the point is to not allow metal to metal contact in those first few cranks.
@@QuantiQualification i hate to say this but no it dont. its made to stick around and not wash away. that why they use it in wheel bearings. its made to resist other oils and water.
@@QuantiQualification i'm not trying to be a smart A$$ but i built engines and worked on anything that has wheels on it my entire life. and did it for a living. until i retired. and just trying to save you some heartache and money later on. but at the same time trying to learn stuff and keep up with the times.
Wait! Did you gap those rings before you put them on the piston? Unless the kit maker pre-gapped them, you have to place them one by one into the bore, measure the gap with the same type feeler gauge you use for valve clearance, and file them to the correct gap. The bore pushes them in just by inserting them and heat expansion closes the gap even more. If the gap is too small the ends of the rings will meet. The rings will stick out too much and scrape all the oil off the bore wall and after a couple hundred miles the heat will destroy that engine. The 143cc kit for sure needs the rings gapped when I installed mine.
It has been a little while but if I remember correctly, I definitely gapped the first 164cc Yuminashi kit I put in after the Takegawa 143cc kit developed piston slap. For the second 164cc Yuminashi kit shown in this video, I didn't gap it since I was worried at the time that I had over gapped the first Yuminashi kit. In later videos where I rebuild a couple more times, I have me measuring the gap on video. Ultimately, my problem centered almost fully around incorrect fueling, leading to heat failure along with needing to add additional cooling for the HP the 164cc produces.
On the first Yuminashi Piston I destoyed, I gapped the rings, although I might have done it too large, not certain. On the second Yuminashi Piston, which I am showing in this video (which also was destroyed by me) I kept the original ring gap from Yuminashi. It is generally recommended to measure and adjust rings if you know how to do it properly. I tried on the first one but my failures appear to not be ring gap related . . . for now at least. There is no mention of a need to gap the rings in the Yuminashi instructions.
Thank you! Takegawa 143cc Big Bore Kit ~$219 (Destroyed Piston, Salvageable Cylinder): Yuminashi 164cc Big Bore Kit #1 ~$125 (Destroyed Piston, Salvageable Cylinder): Yuminashi 164cc Big Bore Kit #2 (Destroyed Piston, Reusing the Cylinder on next trial so only reflecting price of replacement piston) ~$36: So total parts destroyed or no longer used so far is $380. Actual cost of parts actually destroyed would be 3 pistons at ~$108 so not too bad.
Wanted more speed out of the bike so I threw in a Takegawa 143cc Big Bore Kit. Followed everything by the letter but still ran into problems after running the bike for a while.
Just got my Trail 125 and also live near a high-speed area. I've just been taking back roads but never considered a BBK option...How's this newest one lasting? Do you have a list of the other mods and where you purchased? Throttle body, fuel-injector, oil-pump, any changes to the stock sprockets?
The newest cylinder is from Kitaco and it is doing great! I just put up a video where I swapped in the old exhaust just to see what it does. The next video I put out will be my final 164cc setup that I have been running along with all the part numbers, costs, and links to the go faster bits. Then I get to (finally) start talking fun accessories!
Thought about that, but I think the engine will still turn since the auto clutch is disengaged on this one unless the engine is turning sufficiently. I could be wrong, however. I just put the engine back together last night. Great suggestion to try. I just missed the opportunity.
@@QuantiQualification Opps! You're right! What I'm describing only works on a manual cable/hydraulic actuated clutch. If you tried to do what I said, it would be like the engine was idling at a stop, with no connection between the engine and the rear wheel.
You are absolutely correct. It is definitely better not to have to rinse the grease into your motor oil after it first starts. I transitioned over to oil in later builds.
I had around 250 miles, I believe, before I started modifying the original motorcycle. The motorcycle worked perfectly but just couldn't go fast enough. The first cylinder and piston I put in, a Takegawa 143cc, lasted a couple of hundred miles before it developed piston slap. Worked great before that. Developed piston slap immediately following a high speed, tucked run, at 70 mph.
a few things i notices which will cause the piston to be destroyed... 1. Upgrade the oil pump for increase the oil flow to the cylinder head, failure to do this will cause 2. seizing of the engine ( Failure to set the piston ring gaps can also cause the engine to seize if it gets too hot ) I notice that your still running the stock air intake ... is the cylinder head intake ported to match the manifold, also is the exhaust ported to match the exhaust header., as these can also cause issues with overheating especially the exhaust port. ( The majority of big bore kit failures are due to under-lubrication which causes the piston to overheat and seize. )
So far, increasing the fuel injector size has helped prolong the life of the latest piston. Good point on increasing lubrication. At some point I may get a higher flow oil pump installed. In the mean time, I am using some good Ester based oils.
@geoff james In my case, the stock fuel injector was not able to supply enough fuel at high rpm wot situations. The map itself I think was okay, the fuel injector itself just couldn't keep up.
@@QuantiQualification that's correct.... there are 2 options, (A) re-tune the fuel map or (B) upgrade the injector.... ( most people opt to the 2nd option due to not having access to the tuning software and a Dyno Tuner. Heat and Stress are the biggest killers ( which is easily overcome with the increased circulation and increased oil quality, (plus addition of oil coolers for the extreme). With your engine you have replaced the piston and cylinder twice but still have not addressed the likely cause of why these parts have failed. Everything is relevant, Engine RPM, Duration of ride, Ambient weather conditions, Undulation of roads, how much load / stress you place of the engine, these factors will dictate the reliability, whereby if your still experiencing an issue then you must analyze the problem as being from Excessive RPM, vibration, heat or lubrication related, and then address it accordingly. ( My own bike has BBK, Ported head, Air intake Upg, Exhaust Upg, Oil pump Upg, Injector upg, Ecu Upg, Balanced Crank Upg (13,000rpm) I do a lot of highway riding at 110-120Kph for extended distances and having no issues.
@@geoffjames2875 Excellent points. I will take your advice and upgrade the oil pump as one of the next things. I do want it to be reliable. I will also be figuring out some wideband tuning so I can get the map exactly right as well. Thank you for the input!
Thank you for sharing ! Very well done ! Just curious what was done to clean out the lower part of the engine if it was contaminated with metal . Could the metal get into the bearings etc....? Thank you !
The metal absolutely will get into the bearings and get pumped throughout the engine. What I did after the first 164cc kit self-destructed and prior to disassembly was add fresh oil and then spin the engine prior to draining it. Then, this morning, after a brief warm-up, drained the oil again. Added fresh oil for a third time, went for a short ride, and drained it again. So that is three flushes to get as much of the metal out as possible. I will now ride it for about 140 miles of break-in and then drain it for the last time. Should be all good from there, assuming it doesn't blow again 😅. Good thing this motorcycle takes so little oil or the above procedure would have been expensive!!!
@@QuantiQualification Thanks for that explanation . Very interesting scenario that you are doing a great job at repairing . I first thought that the motor was done but I feel your doing the right things and so far its working better then I would have thought . I am currently trying to decide whether to buy a new 125 Trail and when I seen what happened to yours I almost shed a tear but I'm sure you will get it back to normal . Great explanations throughout your repair . Thank you
@stew tube The Trail 125 is such a great bike. I recommend it highly. Around here, I need it to do at least 55 to 60 mph as all roads out from my house have this limit. Stock it did between 51-52mph average. So far, the fix is working. I have done 10 miles with a max speed of 35mph, 20 miles at 40 mph, and 30 miles at 45mph. I will keep working my way up to top speed, breaking in the piston and cylinder as I go.
You are absolutely correct. Cylinder scoring as well is a bad deal. I try it in a later video, and although it was great and cheap for testing, I ultimately replaced it.
Very well done video with all the detail a hobbyist needs, without any of the filler. Thank you.
Thank you. Much appreciated!
Thank for sharing the breakdown. And rebuild back up You did it very well. Never thought that it had a big bore kits so soon. For the CT 125.
Thank you! i thought it would be fun to show the process and failures that can occur while trying to upgrade performance without the use of a dyno or other expensive diagnostic tools. Tearing the bike apart and then rebuilding is part of the fun! This is the first time I have tried to do something like a big bore kit for a fuel injected cycle. I have some successful experience with two-strokes using carburetors. There it was simply changing jets.
@QuantiQualification Very true two stroke is jetting n reeve valve setting not really that complicated. Pretty straight forwards.wiyh carb.
I almost laid an egg when you put grease in the cylinder!
LOL! You would definitely need some grease for that (the egg)! Realistically, the grease will wash away in the first few cranks of the cylinder. Oil is a better choice but the point is to not allow metal to metal contact in those first few cranks.
I enjoyed your video...I did this on an old Bentley 90 when I was kid took it to 107 it made a difference
Wow, 107 sounds super-fast for an old Bentley! Bet it was seat-of-your pants exciting!
Good video thanks, same big bore kit I want to do. But you need Assembly Lube! driving me crazy with that grease 😁
LOL! Yep, I will never live the grease bit down.
WOW axel greese for the wrist pin and cylinder walls. i just hope it dont gel up and gets as hard as a brick once it gets hot
Motor oil is definitely a better choice but the grease rinses away with the circulating oil in seconds after start up.
@@QuantiQualification i hate to say this but no it dont. its made to stick around and not wash away. that why they use it in wheel bearings. its made to resist other oils and water.
@@MadsWorld34 Fair point and noted.👍
I have now added a note in the description as such.
@@QuantiQualification i'm not trying to be a smart A$$ but i built engines and worked on anything that has wheels on it my entire life. and did it for a living. until i retired. and just trying to save you some heartache and money later on. but at the same time trying to learn stuff and keep up with the times.
Wait! Did you gap those rings before you put them on the piston? Unless the kit maker pre-gapped them, you have to place them one by one into the bore, measure the gap with the same type feeler gauge you use for valve clearance, and file them to the correct gap. The bore pushes them in just by inserting them and heat expansion closes the gap even more. If the gap is too small the ends of the rings will meet. The rings will stick out too much and scrape all the oil off the bore wall and after a couple hundred miles the heat will destroy that engine. The 143cc kit for sure needs the rings gapped when I installed mine.
It has been a little while but if I remember correctly, I definitely gapped the first 164cc Yuminashi kit I put in after the Takegawa 143cc kit developed piston slap. For the second 164cc Yuminashi kit shown in this video, I didn't gap it since I was worried at the time that I had over gapped the first Yuminashi kit. In later videos where I rebuild a couple more times, I have me measuring the gap on video. Ultimately, my problem centered almost fully around incorrect fueling, leading to heat failure along with needing to add additional cooling for the HP the 164cc produces.
Top video mate
Thank you! I appreciate the support.
Are the rings pre gapped?? Or did you gap them?
On the first Yuminashi Piston I destoyed, I gapped the rings, although I might have done it too large, not certain. On the second Yuminashi Piston, which I am showing in this video (which also was destroyed by me) I kept the original ring gap from Yuminashi. It is generally recommended to measure and adjust rings if you know how to do it properly. I tried on the first one but my failures appear to not be ring gap related . . . for now at least. There is no mention of a need to gap the rings in the Yuminashi instructions.
a great learning channel.total damage $ ?
Thank you! Takegawa 143cc Big Bore Kit ~$219 (Destroyed Piston, Salvageable Cylinder): Yuminashi 164cc Big Bore Kit #1 ~$125 (Destroyed Piston, Salvageable Cylinder): Yuminashi 164cc Big Bore Kit #2 (Destroyed Piston, Reusing the Cylinder on next trial so only reflecting price of replacement piston) ~$36: So total parts destroyed or no longer used so far is $380. Actual cost of parts actually destroyed would be 3 pistons at ~$108 so not too bad.
What happened to it to make the upgrade necessary? I thought they were bullet proof
Wanted more speed out of the bike so I threw in a Takegawa 143cc Big Bore Kit. Followed everything by the letter but still ran into problems after running the bike for a while.
Just got my Trail 125 and also live near a high-speed area. I've just been taking back roads but never considered a BBK option...How's this newest one lasting? Do you have a list of the other mods and where you purchased? Throttle body, fuel-injector, oil-pump, any changes to the stock sprockets?
The newest cylinder is from Kitaco and it is doing great! I just put up a video where I swapped in the old exhaust just to see what it does. The next video I put out will be my final 164cc setup that I have been running along with all the part numbers, costs, and links to the go faster bits. Then I get to (finally) start talking fun accessories!
If you don't want to do the Breaker Bar/Torque Wrench juggle next time...put the bike in gear and apply the rear brake.
Thought about that, but I think the engine will still turn since the auto clutch is disengaged on this one unless the engine is turning sufficiently. I could be wrong, however. I just put the engine back together last night. Great suggestion to try. I just missed the opportunity.
@@QuantiQualification Opps! You're right! What I'm describing only works on a manual cable/hydraulic actuated clutch. If you tried to do what I said, it would be like the engine was idling at a stop, with no connection between the engine and the rear wheel.
@@steverandall5814 👍
Light oil is better for assembly of piston through the cylinder and pin 📍 ❤
You are absolutely correct. It is definitely better not to have to rinse the grease into your motor oil after it first starts. I transitioned over to oil in later builds.
How many miles did the engine do before you had to put a new piston and rings?
I had around 250 miles, I believe, before I started modifying the original motorcycle. The motorcycle worked perfectly but just couldn't go fast enough. The first cylinder and piston I put in, a Takegawa 143cc, lasted a couple of hundred miles before it developed piston slap. Worked great before that. Developed piston slap immediately following a high speed, tucked run, at 70 mph.
Are they pre gapped rings?
No, unfortunately not.
a few things i notices which will cause the piston to be destroyed... 1. Upgrade the oil pump for increase the oil flow to the cylinder head, failure to do this will cause 2. seizing of the engine ( Failure to set the piston ring gaps can also cause the engine to seize if it gets too hot )
I notice that your still running the stock air intake ... is the cylinder head intake ported to match the manifold, also is the exhaust ported to match the exhaust header., as these can also cause issues with overheating especially the exhaust port. ( The majority of big bore kit failures are due to under-lubrication which causes the piston to overheat and seize. )
So far, increasing the fuel injector size has helped prolong the life of the latest piston. Good point on increasing lubrication. At some point I may get a higher flow oil pump installed. In the mean time, I am using some good Ester based oils.
@@QuantiQualification Increasing the fuel injector only saves you from having to retune the fuel map in the ecu.
@geoff james In my case, the stock fuel injector was not able to supply enough fuel at high rpm wot situations. The map itself I think was okay, the fuel injector itself just couldn't keep up.
@@QuantiQualification that's correct.... there are 2 options, (A) re-tune the fuel map or (B) upgrade the injector....
( most people opt to the 2nd option due to not having access to the tuning software and a Dyno Tuner.
Heat and Stress are the biggest killers ( which is easily overcome with the increased circulation and increased oil quality, (plus addition of oil coolers for the extreme). With your engine you have replaced the piston and cylinder twice but still have not addressed the likely cause of why these parts have failed.
Everything is relevant, Engine RPM, Duration of ride, Ambient weather conditions, Undulation of roads, how much load / stress you place of the engine, these factors will dictate the reliability, whereby if your still experiencing an issue then you must analyze the problem as being from Excessive RPM, vibration, heat or lubrication related, and then address it accordingly.
( My own bike has BBK, Ported head, Air intake Upg, Exhaust Upg, Oil pump Upg, Injector upg, Ecu Upg, Balanced Crank Upg (13,000rpm) I do a lot of highway riding at 110-120Kph for extended distances and having no issues.
@@geoffjames2875 Excellent points. I will take your advice and upgrade the oil pump as one of the next things. I do want it to be reliable. I will also be figuring out some wideband tuning so I can get the map exactly right as well. Thank you for the input!
Thank you for sharing ! Very well done ! Just curious what was done to clean out the lower part of the engine if it was contaminated with metal . Could the metal get into the bearings etc....? Thank you !
The metal absolutely will get into the bearings and get pumped throughout the engine. What I did after the first 164cc kit self-destructed and prior to disassembly was add fresh oil and then spin the engine prior to draining it. Then, this morning, after a brief warm-up, drained the oil again. Added fresh oil for a third time, went for a short ride, and drained it again. So that is three flushes to get as much of the metal out as possible. I will now ride it for about 140 miles of break-in and then drain it for the last time. Should be all good from there, assuming it doesn't blow again 😅. Good thing this motorcycle takes so little oil or the above procedure would have been expensive!!!
@@QuantiQualification Thanks for that explanation . Very interesting scenario that you are doing a great job at repairing . I first thought that the motor was done but I feel your doing the right things and so far its working better then I would have thought . I am currently trying to decide whether to buy a new 125 Trail and when I seen what happened to yours I almost shed a tear but I'm sure you will get it back to normal . Great explanations throughout your repair . Thank you
@stew tube The Trail 125 is such a great bike. I recommend it highly. Around here, I need it to do at least 55 to 60 mph as all roads out from my house have this limit. Stock it did between 51-52mph average. So far, the fix is working. I have done 10 miles with a max speed of 35mph, 20 miles at 40 mph, and 30 miles at 45mph. I will keep working my way up to top speed, breaking in the piston and cylinder as I go.
Any scratches on a piston are not good.
Even the smallest scratches.
You are absolutely correct. Cylinder scoring as well is a bad deal. I try it in a later video, and although it was great and cheap for testing, I ultimately replaced it.
i have allways oil a cylinder not grease
Thank you and agree. I switched to oiling the cylinder rather than greasing after another comment similar to yours.
Should of left it alone
LOL, perhaps! 🙂