YD100 Motor questions

[lazar26]

So I’ve recently just got around 300 miles out of my eBay motor, (bought the motor kit from a guy missing a lot of parts.. very so it’s frankenstein’d together..). However I *think* I think one of the rings are broke/breaking. Still runs great but has a tap or a chatter. Changed out the head and head gasket which fixed a lot of the chatter but alas, still sounds similar to a blender. I will just ride this guy until she blows! Put 10 miles on it today alone with said issues. It is my first self built motor bike, I beat the living CRAP out of it. I learned a lot on it. I’m honestly surprised it lasted this long.

Anyways, I plan to rebuild once this goes and sell it. For now I will continue to beat the heck out of it riding around campus. For my personal bike, I want something that’s a little more comfortable going town traffic speeds (average 35mph in my area). How does the YD-100 stand up? With a 36T. I haven’t seen many posts about it around. Anyone have personal experience with this motor? I already ordered the kit at a pretty good price! I’m looking more for longevity if possible, of course I will baby this thing a lot more after I already had my fun breaking one. Some advice for not torching the rings on this? I was running a 16:1 first 200mi, 25:1 thus far.

My friends and I are really getting a lot of enjoyment out of this hobby! I hope to learn more as I go! Pictures below are of the bike as well as what my father says is a scored jug.

 

[Chainlube]

If you had the head off, why didn't you just lift the jug off and examine it? They go back on fairly easy. Your jug just looks like the chrome is coming off, did you drag a fingernail over it and see if there are any grooves?

 

[lazar26]

I did take my fingernail over it, it didn’t have any deep scratches that’s for sure. Nothing that caught my fingernail anyway. The chattering only started happening yesterday.

I actually didn’t know that the jug came off so easy until researching it today after my ride. I’ll plan to do that probably tomorrow or sometime this week if I get ambitious. I mean a new jug and piston set is all of $20 so I don’t mind blowing it and rebuilding. That’s part of the fun right? Haha.

Now that you mention chrome, I did find some small bits of metal like substance on the head surface near the head gasket upon inspection. Circled in the picture below. It wasn’t magnetic.

 

[Chainlube]

Before you buy a new piston, you have to confirm whether yours has a low hole or a high hole for the wrist pin. If you get the wrong piston, you either have very little compression or you're banging into the top.

 

[lazar26]

Okay, thank you for the advice!! I’ll tear it down in the next few days to check. Glad I joined the forum, already very helpful!

 

[PCWOOD]

I saw today on go maxs' website that you can get 32 tooth sprockets with the engine kits. Only some have the option. The videos I watched today of test running the 32 tooth sprocket worked fine in Johnson city, TN (the mountains). But he was at full throttle too.

 

[ImpulseRocket]

Generally speaking a YD100 is a single piece head/Jug. The weird thing is that doesn't look to be an LD100 either... weird

As far as achieving top speeds in the 30's it is very possible with the YD/LD motors. Sprockets can only do so much if the motor can't pull you there to begin with. Some basic port matching and cleanup work at the transfers and setting the squish gap around 0.9 to 0.7mm will do a lot to help boost that engines overall efficiency and performance to get you there without getting into more complicated porting. I would suggest finding head gaskets that match the bore of the cylinder a little better than the current one I see in the picture above that is much wider than the bore. It is one of those small things that on its own may not be a huge deal but adds up with other small things.

Then a good pipe and silencer combined with good carb tuning to get you the rest of the way. Just be aware that you will be pushing the motor pretty hard to hold those speeds.

If you are feeling brave enough to get into proper porting then you can really get in there and start to wake up that engine. The port timing and quality of the ports as a whole on these cheap little engines leave a lot to be desired.

Going along with that port work and usually increased RPMs that go along with it a properly balanced crank is not only nice to have for comfort reasons but also helps the engine run in the higher Revs much more efficiently. It also helps to reduce stress on the bearings.

If the engine is going to be apart for a rebuild it is the perfect time to do it.

Nice bike by the way. I love seeing other non-cruiser based builds on road bike frames.

 

[DAMIEN1307]

I saw today on go maxs' website that you can get 32 tooth sprockets with the engine kits. Only some have the option. The videos I watched today of test running the 32 tooth sprocket worked fine in Johnson city, TN (the mountains). But he was at full throttle too.

Nice bike by the way. I love seeing other non-cruiser based builds on road bike frames.

You guys realise that the "nice bike" was from a post 2 years ago...RIGHT???...lol...Please check the date codes on these posts before replying...This thread is already pretty old so i'm locking it at this time...lol.