Buddy 125 engine replacement

paracer · Post by **paracer** » Mon May 15, 2017 11:03 pm

Curiosity has me thinking.

If a 125 needed a replacement engine. How similar would the stock engine be to a generic short case gy6 150cc sourced off of Ebay, amazon, or another online retailer? The block and transmission assembly look right, but is there anything odd about the rear axle that would complicate things?

What I am thinking is that it might be neat to swap a 125 with a 150, then add a big valve head and a t100 or A9 cam. The cost, if there aren't a whole bunch of other things involved, wouldn't be too bad.

babblefish · Post by **babblefish** » Mon May 15, 2017 11:22 pm

Well, unless the crankcase itself of your 125 were broken, all those things you mentioned could be done to your existing engine thereby forgoing any complications with trying to fit a generic GY6 engine.

JettaKnight · Post by **JettaKnight** » Tue May 16, 2017 5:21 pm

babblefish wrote:Well, unless the crankcase itself of your 125 were broken, all those things you mentioned could be done to your existing engine thereby forgoing any complications with trying to fit a generic GY6 engine.

True. And the Buddy block is going to be of better quality.

paracer · Post by **paracer** » Thu May 18, 2017 11:58 pm

Thanks guys!

I am going to try a couple things this weekend.

The bike was running well until a few days ago. After completing a little carb work last weekend I went to swap the spark plug. However, the cylinder head threads came right out with the spark plug. So, I proceeded to swap in the stock cylinder head. After getting everything buttoned up including adjusting the valves, I fired up the bike. It came right to life, but when I went out for a test ride, I noticed a pretty good knocking noise when I would be riding under medium to heavy throttle. The bikes power felt decent considering the choked down cylinder head.

I'm not sure what happened whether there might be a bit of carbon buildup on the piston that I need to scrape/clean off. It might be slightly contacting the head.

The other thing I don't like is that when I rotate the engine by hand with the spark plug out I hear a bit of noise and grittiness (best word I can come up with) out of the crankcase. I also hear a bit of rattle in there at idle. This has me wondering if my daily riding including highway use over the past year and with the big bore has had an impact and maybe hurt the crank or rod bearings.

If I can't figure something out this weekend, I might be gearing up for that engine swap as it would seem that my issue is then something inside the block. I'm not equipped to handle that kind of repair as I do all my work outside my apartment building.

I will report back this weekend with any news. If worst comes to worst, this could be a thread about how to swap a generic gy6 engine into a Buddy.

paracer · Post by **paracer** » Sat May 20, 2017 11:56 am

I'm pretty sure the issue that I am experiencing is piston slap. I noticed a bit of a polished appearance on the cylinder wall on the upper and lower surface, roughly in the middle of the piston's range of travel.

I pulled the cylinder head yesterday evening and cleaned the carbon deposits off the top of the piston, and around the top edge of the cylinder. The result is what I determined to be much less of the noise I was hearing.

I am going to run a couple changes of Mobil 1 through the engine at a relatively short interval with Sea Foam in both the gas tank and crank case. We shall see what happens.

Meis · Post by **Meis** » Fri May 26, 2017 9:06 pm

The knocking sound could also be detonation or pre-ignition. If the cyl head you replaced with the stock one was larger (read: had a large bowl) then your stock one may have risen the compression ratio to a level that the fuel cannot protect from detonation. Maybe try running some higher octane fuel.

The noise could also be from worn out rod bearings causing excessive movement and allowing the rod to contact the crank case.

paracer · Post by **paracer** » Sat May 27, 2017 12:53 am

Meis wrote:The knocking sound could also be detonation or pre-ignition. If the cyl head you replaced with the stock one was larger (read: had a large bowl) then your stock one may have risen the compression ratio to a level that the fuel cannot protect from detonation. Maybe try running some higher octane fuel.

The noise could also be from worn out rod bearings causing excessive movement and allowing the rod to contact the crank case.

Those are two things I have considered.

I threw a jet in a couple sizes larger before firing up the bike, and I always use premium. I am going to look at the spark plug this weekend to see where I stand.

I have wondered as well about bearings. There's not much I can do there. I would likely replace the engine if a bearing proves to be making the noise.

As it is, I am riding daily to work and back. Nothing seems to be getting worse at the moment. My other wonder is that I might just be hearing a different engine tone with a different cylinder head.

babblefish · Post by **babblefish** » Sat May 27, 2017 7:03 am

What year is your Buddy?

paracer · Post by **paracer** » Sat May 27, 2017 4:14 pm

babblefish wrote:What year is your Buddy?

It's a 2016 with approx. 7k miles. I ride about 20 miles daily with a number of 100 mile days and a 400 mile marathon thrown in there.

I would want to note that I haven't seen any metal flecks in the oil since the very first oil change at about 100 miles into break in.

I'm really leaning towards the sound that I am hearing

You know, with as much history and experience that I have with automotive work I don't have a lot of experience with things going less than planned. I can normally troubleshoot issues without much guesswork. I'm due for something like a bearing failure.

Time to go check the spark plug for detonation and mixture...

paracer · Post by **paracer** » Sat May 27, 2017 4:43 pm

I just checked. The plug was clean. The insulator was a bit too white for my tastes. I put in a larger main jet.

I don't think I upped the compression too much with the stock head. I say that because the starter has no problem turning the engine over.

Right now, all signs point to... ride it!

JettaKnight · Post by **JettaKnight** » Tue May 30, 2017 5:55 pm

paracer wrote:I have wondered as well about bearings. There's not much I can do there. I would likely replace the engine if a bearing proves to be making the noise.

As it is, I am riding daily to work and back. Nothing seems to be getting worse at the moment. My other wonder is that I might just be hearing a different engine tone with a different cylinder head.

A little high pitched rattle could be a top end bearing (on the piston). That's a relatively easy fix that only requires removing the cylinder.

lovemysan · Post by **lovemysan** » Wed May 31, 2017 12:06 pm

2 things rotating the engine by hand the starter clutch will make noise and sometimes it sounds gross. Your not spinning it fast enough to get the weights out of the way. I once bought a mint buddy with a bad crank. Turned out to be the starter clutch was damaged. Also people in my area call my bike "old box of rocks". It has a crank rattle caused by the conrod slop caused by mis aligned crank bearing cups . The big end of the conrod is being chewed off from the side. When I pulled the crank to replace it the stator side of the conrod big end was .050 smaller. Lots of glitter in the oil. Its been making the same noise again for a year now. The bike continues to run fine and will happily pull me to 70 mph+. New engine soon.

One last thing to note: stock I could hear a noise as well, it made a funny rattle sound when accelerating. Almost a preignition It was much louder if I test rode with the valve cover access plastic off. I've ridden a few b125s and learned they all sound that way

babblefish · Post by **babblefish** » Wed May 31, 2017 12:18 pm

Be careful with crank bearing noises. The one in my Blur was making knocking sounds for a while, but otherwise ran fine so I ignored it...until the day the engine seized up while I was riding. Luckily for me, when that happened, the clutch released which allowed the rear wheel to keep turning so I didn't soil my rear end. Turned out that the big end bearing of the connecting rod disintegrated and locked up the crank. This sent metal particles throughout the inside of the engine wiping out the oil pump and scoring the piston and cylinder wall.
Anyway, all's well that ends well. I rebuilt the engine and it's now a 183cc with a bit more spunk than stock.

paracer · Post by **paracer** » Thu Jun 01, 2017 3:57 am

lovemysan wrote:One last thing to note: stock I could hear a noise as well, it made a funny rattle sound when accelerating. Almost a preignition It was much louder if I test rode with the valve cover access plastic off. I've ridden a few b125s and learned they all sound that way

I do run with the front cover removed.

I'm not at this point going to do much else except ride the bike. There wasn't any junk in the oil when I changed it the other weekend. I'm leaning toward this being just a noise that my combination of parts is producing. It's just really weird that it started the moment I switched from the hi-po head to the stocker.