HS 49cc is losing the fight for survival...

Hey everyone,

I have been having some issues with my HS 49cc for the past few weeks, and today I think my engine is finally toast.


Background:

A few days ago I was riding like I always do, when suddenly I heard a rattling noise. I stopped to investigate, and everything was tightened down, so I started it up again. When it was idling, I heard the noise again coming from inside and the engine was showing signs of overheating. I immediately killed the engine and pushed my bike back to my house.

I tore open the engine after it was cool and just as I suspected, the oil slinger had broken off. I inspected the rest of the engine and it was all in perfect shape. I could still even see the crosshatch marks on the cylinder walls from when it was honed. I cleaned it all anyways with purple cleaner, rinsed each part multiple times with water, then stuck them in the oven to dry off. I put all the parts back together, using generous amounts of royal purple motor oil on each part as I put them back together. I then resealed the crankcase and let it dry for a day.

The next day, I started it up on my bench and It ran really well. It revved up fast and sounded beautiful. I stuck it on my bike and made sure everything was aligned and tightened, then took it for a ride. The engine was bogging a bit, so I put it on the stand and screwed in the idle screw so it would run by itself then adjusted the tuning screw for the highest idle speed (this is the method that Phantom Bikes told me to use to tune it, and it has worked in the past).



Problem:
While tuning it the last time, a bunch of white smoke started to fly out of the oil catch and the engine was going down in RPMs. I killed it and looked it over, and the engine was steaming. I thought it was residual oil from when I put it back together, so I started it up again. After 5 more seconds, the engine cut off and I can no longer turn it over. I removed the oil plug and the oil is a clean purple color with no foreign substances in it. The thing is that in another member's thread about the oil slinger, it was said that its not needed due to the big plastic gear that fings oil everywhere. If this engine is dead, then im just gonna build a 79cc predator bike instead but I would love to save this one if possible.


Thanks guys,
Chris N.

scotto- said:

Well I'm finally getting around to replacing the oil slinger I broke off over 7,000 miles ago.

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2door said:

Scotto,
That big plastic gear on the lower end moves so much oil that the slinger isn't really needed. The gear forces oil up through a passage to the rocker arms and there's plenty of oil moving around down below to keep the big end of the connecting rod and wrist pin lubricated. I've seen these engines run hundreds of miles without the slinger.

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Both of these riders say that the slinger is not necessary. Ill open up my engine and see what the problem is next weekend, as school is starting tomorrow

EDIT: I'll post pics of anything I find.

On the HS 4 stroke motors, theres not supposed to be a pin bearing or bushing between the con rod and crankshaft, right? Cause in mine there isn't, and I'm guessing that is where the problem is.

As far as the slinger goes, how do you recommend I make one? It seems like sheet metal would be too thin.

Edit: On the other motorbike forum, alot of people say you should not remove the metal shrouds because the engine will overheat. Could that plus the loss of the oil slinger be causing me problems?

By bigger do you mean wider or longer, or both. Seems after a certain point of making it bigger, the amount of force it takes by slapping the oil 5k times per minute would break it off.

Alright, I have the case apart and I loosened the bolts on the bottom of the connecting rod. Now it spins very easy, but the thing is even if I slightly tighten the bolts, it seizes up again and I cant turn it. How tight do I make these, and if its required what are the exact torque specs?

O_O Well that's not good. Ill go out there and see what the extent of the damage is.

Alright, so I took it apart and found these deep scratches on the con rod and crankshaft. Here are some pics, what do you think? I already know I am going to have to buy new parts, so where do you find the parts for these small engines?


Connecting Rod:




Connecting Rod end cap:




A few different angles of the crankshaft:

I dont think Phantom has engine parts, unless they tear one apart for me. I have been contemplating a 97cc lifan build, and may just switch to one of them now.

MotorBicycleRacing said:

Did your take your bike up to 35 mph?

This is why your connecting rod almost seized, and would have
broken.
Phantom is way under gearing their bikes if they use a 50 tooth
rear wheel sprocket.
They should be using a 36 toother.

The ones I have seen break their connecting rod have been
abused at 10,000 rpm for an extended distance.

Usually a 4G with a 5:1 gearbox and 11? to 50 teeth 26" wheels.

7800 rpm with the above gearing is only 27 mph!!!!

9800 rpm with the above gearing is only 34 mph!!!!

10,000 rpm with the above gearing is only 34.7 mph!!!!

The HS motor will rev that high ......Kaabooom!

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I was actually going 35mph steady for entire rides. Phantom told me that they ride all of their bikes wot and "wind them out till they're screaming" and never had a problem with any of them. I called them up today and Sterling said they have an old engine that has been sitting around that they never use. He said I could take it for 40 bucks and use it for parts or as a engine. I asked if its in good condition and he said yes, so I gonna go pick it up tomorrow.

For the future, what can I do to prevent this from happening? I know over revving is the cause, but it seems that this happens from lack of lubrication. Can I drill a hole in the end cap of the con rod to increase lubrication? Any DIY mods that do not require specialty equipment (cnc, etc) would be great. I also might put JB weld on the part of the slinger that seems to be the weak spot to reinforce it. I am also going to pick up a tach for my bike so I can see what RPMs im running at.

As is my motorbike struggles up hills. If I lower the rear sprocket then I will be pushing my motorbike more than riding it, so that's not an option.