Just a "few" issues with my china girl motorized bicycle....

Spaz_Static

Spaz_Static

New Member
Minor issue #1, she'd been having some idle issues where she'd idle real high, then calm down after a random period of time. Adjusting the idle screw only really affected the low idle (after it got out of it's "fit", shall I say). I assumed it was cause it was breaking in or something. It has progressively gotten worse, idling higher, longer, and once it was done with it's "fit" it would sometimes idle so low it would die. That really started yesterday or sometime recently. That became major issue number 1. Once that started happening, I knew something needed to be fixed. Some searching later I figure it might have to do with the lack of seal between the carb and the intake pipe, so I decided I'd remedy that by getting some black silicone per Norman's suggestion in his rebuild your carb thread. Well, today, a piece of the cylinder gasket BROKE off and is presently sitting on my magneto cover. I poked it, and it's basically disintegrating. That gasket needs to be replaced. I can basically see right into the cylinder now, clearly causing problems.

Minor issue #2 (or #1 if you moved previous minor #1 to Major #1) the exhaust end cap wasn't sitting right from the get go and I decided to see if I could get it sitting even and actually seal more (or at all), well, here comes some more issues. Once I looked inside the muffler, I see a **** job of welding the screw to the end of the exhaust pipe (it's being held on by maybe as much as .5 square cm, probably more more .25) and it's crooked which is why the cap wasn't sitting pretty. Looking deeper, the pipe on the end cap has bent a couple of the bracing rings inside. Also, as I loosened the screws to take off the exhaust, the gasket broke in two... That's another gasket that needs to be replaced, it also explains the minor amount of spent fuel that has been very slowly accumulating under the exhaust port. The muffler/exhaust pipe probably just needs to be replaced, but I may be able to remedy it with some work...

Minor #3, the tiny gasket for the screw for the fuel bowl drain that came with the engine was too big and didn't seal. I replaced that with an aluminum one that I fashioned out of some aluminum sheeting, and it seems to be doing ok, but could probably due to be replaced with a normal gasket.

... I think that's all for now. We'll see how things go once the gaskets get replaced and I get her back together.

-Spaz
 
Re: Just a "few" issues with my china girl....

You didn't say what motor kit you have, but all those problems are common on a china girl, and easy to fix.

I don't run a lower exhaust bracket and had 3 exhaust gaskets go bad on my 80 in about 400 miles, till changing to a sbp xpipe.

I bought gasket material at a auto store and make my own intake gaskets. They're pretty easy to make.
 
Re: Just a "few" issues with my china girl....

Oh, sorry, I did manage to leave that completely out somehow lol

48 cc BoyGoFast 2 stroke straight head, stock everything thus far (except the aluminum fuel bowl gasket and a steel strap securing the aft of my chain guard).

Yeah, I was thinking I would just get some gasket material from the local auto shop and cut my own but I don't know which type, they have several (rubber, rubber and cork, rubber and cellulose, etc.)... and as for the poor state of the exhaust, I am thinking about just replacing the whole thing with an expansion chamber.
 
Re: Just a "few" issues with my china girl....

Spaz_Static said:
Oh, sorry, I did manage to leave that completely out somehow lol

48 cc BoyGoFast 2 stroke straight head, stock everything thus far (except the aluminum fuel bowl gasket and a steel strap securing the aft of my chain guard).

Yeah, I was thinking I would just get some gasket material from the local auto shop and cut my own but I don't know which type, they have several (rubber, rubber and cork, rubber and cellulose, etc.)... and as for the poor state of the exhaust, I am thinking about just replacing the whole thing with an expansion chamber.
Click to expand...

O'Reilly auto supply sells a package of several different kinds and thickness gasket materal for a few $.

Use the search box on this site to look up head gasket failures, and you'll get a lot of information.
 
Re: Just a "few" issues with my china girl....

Both one and two are from gasket failure. You can use silicone, a paper gasket, or a better screw for the third.
 
Re: Just a "few" issues with my china girl....

Some planned fixes are to replace all bolts/etc with higher quality like this, and as for the cylinder gasket, should I order one premade specifically for these engines, or should I just go to Autozone and grab some gasket material and cut one out myself? If the latter, then what type of gasket material should I use, they have several different types available listed here. As far as the exhaust gasket, I think I had a spare come with my kit, but that one will probably break like the old one, hah. Should I just use it, or should I get a new one/make one? Again, if the latter, what gasket material should I use? I'm also debating getting an expansion chamber exhaust... I have a 41 tooth rear sprocket. I'm also needing a mirror but I'm concerned about vibrations rendering it useless... and pondering disk brakes... I should make a different thread for all that lol.

Anyway, what should I do as far as the gaskets go?

[edit] I need to go to sleep, I'm rambling a bit... also, 20th post, I'm no longer labeled as a newbie!.. though it doesn't change the fact that I am one, lol
 
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Re: Just a "few" issues with my china girl....

It's a great thing to replace all the bolts, definitely do it.

For the head gasket, I recommend using the stock aluminum style, they're just a buck or two, and get a few.

For the base gasket and exhaust gasket, go to a dirtbike shop and ask for a roll of their highest temp gasket material. You won't find as high a quality product at an auto parts shop.

For mirrors, if you let them hang below the handle bars, they don't vibe as much.

Definitely get the disc brake setup - but also, get a sprocket that mounts on the disc brake mount, and get a top hat adapter so you can use disc mounted sprocket and a disc brake rotor.

Lol, it's your thread - bring up whatever you want!
 
Re: Just a "few" issues with my china girl....

NOOOOO, I accidentally went "back" a page and lost everything I had just typed up. :(

So, here is the shorter "don't want to type all that again" version:

New gasket is on, seems to be doing just fine. Thanks to Norman for his thread as it helped me figure out a couple things such as a good method for tracing a new gasket, and how much torque to put on the headbolts. A holepunch is a wonderful way to make the bolt holes, perfect size and using the exacto-knife is a pain at best when trying to cut such small holes.

I took off the busted gasket on the end of my exhaust pipe and filed down the metal protruding from where they punched the mounting holes. Currently I have the exhaust mounted bare on the engine. I'll be using some high temp RTV silicone gasket stuff after I get my hardware kit. I also managed to lose my endcap nut, so when I tested to see how my gasket would do, if it would blow out right away, my bike was loud as ... well, it sounded like a dirt bike and I expect I violated some noise ordinances especially since it was like 3:30 AM.

But good news, gasket held for my 5 minute test ride. I'll do more extensive testing later.

TODO:
  • expansion chamber, will probably get one after my next paycheck.
  • figure something out for lights. I do NOT want a battery or anything, I want them to be powered solely by my engine.
  • speedometer
  • mirrors
  • disk brakes
  • thumb shifters. My handle grips have flanges that make it difficult to get to the shifters, and the throttle makes it all but impossible to get to one of them.
  • remove all the stickers on my bike. It isn't a Mongoose Switchback anymore, so no need to advertise it as such.
  • fresh black paint
  • decals or something to show her name. I've decided to call her NIB after the Black Sabbath song. I love Sabbath. One of the 'interpretations' is "Nativity in Black" and since she's my first and black, I think it kind of fits. Nib is actually reference to Bill Ward's goatee which was shaped like a pen nib. Well, I also have a goatee, not similarly shaped, but still.

If anyone has any suggestions as to anything in that list, I'm open to them.


also, I ended up typing basically everything again anyway... oh well.
 
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Re: Just a "few" issues with my china girl....

I found my end cap nut! It was rolled up in a paper towel. Anyway, end cap is back on, and it sounds a little different now. *shrug* I also think I'm getting a lot of four stroking which I had been getting before, but as the engine was breaking in, it was getting better about every ride, but I'm not positive. There is a marked power loss and the engine sound changes. I don't know how else to describe it.

...just looked it up on youtube, four stroking is exactly what's going on.
 
Re: Just a "few" issues with my china girl....

Trying to address the four stroking issue. I have the NT carb. my needle has 5 slots, and from what I've read, they normally only have 4? Either way, it had been in slot 3, the middle most slot. I tried moving it up (clip up means needle down, resulting in a leaner fuel/air mix, correct?) to second from top slot, and didn't see a notable difference. I then tried moving it to the top most slot, and my engine would idle very high, no matter what I did with the idle screw. I have moved it to second from bottom and it was smoking constantly as well as four stroking except at 100% WOT. I'm still running my break in fuel/oil mix of 16:1 by the way. But I'm not sure what to do, second from top slot, leave it in the middle slot, I'm sure as heck not going to leave it in the top slot, I'd probably burn out my engine. I'm also wondering if I should really even bother, I tend to ride WOT most of the time anyway... also, I tend to four stroke a bit even at WOT when my engine first fires up until it gets just a bit warm, maybe the first 2-4 minutes depending on the temperature outside. Should I adjust my jet, or is that fine?

Thanks for the help guys, you're really making this a lot of fun. ... well, it would be a lot of fun regardless, but your help makes it a lot less of an aggravation. :)
 
Re: Just a "few" issues with my china girl....

Except now in the 2nd highest position I seem to have the idle still high, but it still four strokes... it's almost like in all my meddling I managed to shorten up the throttle cable, which I haven't, I checked it like 12 times in various places... Now I'm just getting confused.
 
Re: Just a "few" issues with my china girl....

OK, so I was readjusting my brakes earlier today after installing the dual pull brake lever from SBP, and I noticed that all four of the spring tensioner housings were split (the plastic covers for the screw adjust for making the brakes pull away from the rim). Now I'm trying to decide if I go on and shell out for disk brakes now, or later (I intend to get them at some point) and if I should just try to superglue the plastic back into a sold ring for the mean time..?

I also don't know what all is required for disk brakes, if I need to do some mods on the front fork or rear stays, which is a good brand, if I need an adapter, or etc... can I get some help with that? I'm likely gonna see about trying to get my bike to a local shop to see what they have to say, but I'm a little afraid I'm going to get "boo"ed out the door as a cheater, or like my bike is an illegitimate... well, you get the idea... but hopefully they'll be professional about it.
 
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