My First Motorbike Project

[lowracer]

Gera,
When I was running the 3 cags, I only used 4 of the 5 mouting points under the engine...I wouldn't worry about it.
-Lowracer-

 

[gera229]

Ok, I obtained a larger bolt today so I'll drill and tap it a size bigger anyway since I already got the bolt.

One other problem:
The fuel that spits out of the exhaust ironically fly's forward and leaves black spots on my shirt and makes it smell like fuel. It's ironic because that fuel is supposed to fly backward, but I suppose this is due to a vacuum like suck from the back as I go forward and pull the air towards me.
Correct me if I am wrong and let me know if you have a possible solution.

 

[gera229]

One of the bolts on my cylinder head decided to strip.

I road my motorized bicycle and realized it wants to bog down and wouldn't idle so it stalled. The max speed just didn't want to go over 20mph or so, so that's when I checked and found a stripped cylinder head bolt.

I attempted to ride it another 3 miles to get home and while it is bad for the engine if done continuously, 3 miles should not have been enough to be harmful in the long run. So I hope nothing happened to my engine as a result of my terrible decisions and it does look like nothing really happened because once I got home, I pulled the starter and had the engine revv a little when giving it throttle and also pull me. So as you can see, it works and starts up while giving it throttle so I would assume nothing bad happened cylinder/piston wise, so it's not a major concern right now. I did peddle quite a bit to help it and turned the engine off tree times on stops on my 3 mile trip home from when 1 of the cylinder head bolts' stripped.

What is the best way to repair it?

Also this is what the plug looked like when I took it when the engine stalled on me (So yes, when I didn't ride it home yet. The beginning of the 3 miles):

Does this greyish color indicate a perfect mixture?

 

[lowracer]

Gera,
I had one of my head bolts strip the case on cag #3. If you are using the longer headbolts like I suggested, you can buy a nut from your local hardware store to fit the one that stripped. There is enough threaded portion of the headbolt poking through the case to get a nut onto the other side of the headbolt & case...I also used a few real small washers to space the nut away from the case to get the nut to mount flush...Just make sure to torque them all equally once reassembled. If you need a pic, I'll have to do that tomorrow since I'm done with the garage for the day...
Spark plug looks good.
-Lowracer-

 

[gera229]

I remember that! My lower bolt stripped.

Did your bolt strip upper or lower? I hope there is enough space for nuts for both sides!

I was gonna think helicoil insert, but then I'd need the right tap which costs ALOT.

I'm glad I'm not the only one spending a lot of time in my garage lol, and hope these gases produced by these engines are not too toxic for human health.

 

[gera229]

I found an amazing deal from China:

http://www.ebay.com/itm/Helicoil-Th...ultDomain_0&hash=item19cbb2f6c6#ht_500wt_1180

But this looks even better:
http://www.ebay.com/itm/25-Piece-Th...ultDomain_3&hash=item5ae8eaac6f#ht_542wt_1163

 

[gera229]

I used an M5 size nut and drilled and tapped it to M6 size.
M5 size nut was a perfect fit, although since you used an M6 size nut that would work too for a more tight fit and less likely to unscrew randomly by itself at any moment.
But I don't think the M5 would unscrew by itself either so either size will work. M6 is certainly easier because you don't have to re-tap it, but I just didn't have a good M6 nut so I did an alternative:

Lowracer, I would still like to see the pic of your nut whenever you have a chance to take it!
This is actually an excellent solution, thanks to you for the idea. It took less than an hour, and I think is far more reliable than stock, because the stock threading just strips too easily.

 

[lowracer]

Gera,
Thanks...
Mine looks exactly like yours does. Use a bit of red loctite on them threads & it should stay put.
Mine was also the exact same hole!
-Lowracer-

 

[gera229]

Did you use an M5 (re-tapped to M6) or did you use an M6 and it fit just fine?

I ask because I used an M5 and retapped it, but if I want to do this to all the mounts then I would like to know if an M6 size would fit.

Thats why I asked for a picture of yours lol. To see how the M6 nut fits in comparison to the M5 I used.

 

[lowracer]

I took one of my longer headbolts down to ACE hardware & used their handy bolt & nut sizing guage they hang on the wall to figure out the correct nut size (cant remember now what that size is). Then I bought the nut I needed for like 20 cents...easy fix
I would never try to retap anything that costs 20 cents....I wouldnt try to retap anything unless it was a very expensive piece & there was no other way to get around the retap.
-Lowracer-

 

[gera229]

Lowracer, you didn't get my point for using a smaller M5 size did you?
These bolts are sized M6. As you see in the picture where the nut is, it's almost hitting the wall so there is very minimal space. I felt like an M6 nut wouldn't fit because its outside diameter is larger than an M5 nut so I felt it just would not even go in without causing some bends, damages, or even just scratches to the aluminum walls there.

But it looks like it worked for you, so I'm guessing an M6 size nut would work too.
Did it cause an scratches to the aluminum walls or anything minimal though?
That is my question: how well did the larger and right sized M6 fit?

That is why I asked for a picture.

 

[lowracer]

I moved it out with a washer or two to get it away from the aluminum walls

 

[gera229]

I see, but the washers don't seem like they will fit either. They are large. You probably drilled larger holes in smaller washers to fit them through there.

A picture would show everything, I really want to see it. It will show me everything. Thanks.

 

[lowracer]

Used small washers (barely larger than the 5mm socket head button)

 

[lowracer]

Gera,
I went into the garage & opened my box of spare cag engines & parts. This engine is disassembled (forgot I took it apart) so I was unable to take pics for you. I guess I figured since I had 2 unstripped cags, I'd only use this one if they both went bad...
I am going to run a cag again on the new DH bike I just bought...I posted a few pre-motorized pics just a few minutes ago on my thread.
-Lowracer-

 

[gera229]

I'd put a nut on each side because now I can't trust the aluminum casing threads anymore. I didn't strip them personally, it stripped on its own maybe because I tightened it too hard and aluminum gets soft when it's hot.

But otherwise, I think if I want to put a nut on each side I'd use an M5 again and re-tap it to M6 just to avoid the nuts there.

 

[happycheapskate]

If you are using allen head bolts, and a nut on the top of the engine mount, why not use the allen head bolt going the other way, and secure it from underneath with the nuts?

 

[lowracer]

Gera,
I has a similar situation happen on the good cag I just installed onto The Banshee. I broke one of the 4 bolts in the engine case that mounts the clutch drum housing onto the engine. I drilled out the broken bolt with a 1/4" drill bit (slightly larger than the 10mm bolt that snapped. There is very little room behind the back of where the threads are between the cylinder jug & the clutch area. I took the nut, put it in a pair of vice grips & filed a few mm off the nut to thin it some & was just able to get it behind there to bolt that 4th bolt through & hold tight...
See Pic
-Lowracer-

 

[lowracer]

Gera,
You were using a 5:1 pocket bike transmission, right?
Please let me know what you think of it & what you put inside it for lube?
I got one that I'm starting a project with & want to make sure its not a hunk of junk.
Thanks,
-Lowracer-

 

[gera229]

Upon opening that transmission it was a 3:1 single chain driven transmission with lots of grease in there. I didn't lube it up, because I thought the grease was enough.

It never broke on me, but I think it is a little noisy. Can't go wrong for $25, that is if the noise doesn't bother you. I got mines off of ebay with free shipping.