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Old 10-07-2006, 05:05 PM   #1
evoboy OP
Artful Bodger
 
Joined: Oct 2006
Location: Coventry, UK
Oddometer: 3
broken cylinder head

loving the site by the way guys

well, i recently purchased a aprillia sr50 '95 model with a leo vinci pipe.
it seemed very loud, so took a look at the manifold and its missing a bolt, and not only that, took the thread off the cylinder head , completely broken it off, and sorta pulled through the pipe where it mounts to the exhaust port.

i havent ridden the bike anywhere yet (im 16 and i was going to ride it on L plates, im in the uk), is there anything i can do to avoid buying a cylinder head? ive kinda bodged it for now by using a washer onto the remaining 'wing' of the exhaust port and then using the nut and bolt to try to close the gap between the pipe and block, but i know this wont last long.

any help greatly thanked guys, help a young un get into the motorbike world
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Old 10-07-2006, 06:11 PM   #2
wildwilly
Old Fart
 
Joined: Oct 2006
Location: Seeley, CA (Alkali Flats)
Oddometer: 149
If I understand you correctly, the threads in the bolt hole of the cylinder are stripped out. Easy and inexpensive fix...take the bike to your local machine shop and they will Heli-coil the bolt hole. Your shop may recommend that the other exhaust bolt hole be heli-coiled, also.
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Old 10-07-2006, 07:22 PM   #3
GreaseMonkey
Preshrunk & Cottony
 
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Joined: Jun 2006
Location: The only county in Illinois with no train tracks
Oddometer: 5,268
Evo,

Does your cylinder look like this?


And I believe we are looking at the exhaust port there.

Is your bolt hole stripped out, or is the ear completely broken off?

If the ear is broken off, unfortunately you will most likely need to replace the cylinder. Sure it can be welded but there is a bit of work involved in doing that, especially if you don't have the broken piece.

If the hole is stripped, best way is to have a helicoil installed, but 2 cheaper options (seeing as money is a bit tighter at 16 than when you are older) are to drill it bigger and tap the next size larger bolt thread, or if you can fit a nut behind the flange you can use a smaller bolt and just tighten it down that way.

There is an RTV silicone sealer made for exhausts, it is usually red or gold color. That may buy you some time right now if the gap isn't too big but try not to rely on RTV too much in your transportation future!

Good Luck!

Also, I got the pic from this page-
http://www.speednspares.co.uk/acatal...rox_70cc_.html

Where they sell a big bore 70 cc cylinder and piston for 71 quid, might be more interesting to do that than to pay money to get teh old one fixed.
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Old 10-08-2006, 02:18 PM   #4
evoboy OP
Artful Bodger
 
Joined: Oct 2006
Location: Coventry, UK
Oddometer: 3
cheers for the help so far

the ear has been broekn completely off, ill try some rtv sealant or exhasut putty around the manifold to try to seal it for now till i can afford a new cylinder head.

and 70cc is not really an option unless i want to be fined more money by the cops .
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Old 10-10-2006, 03:40 PM   #5
evoboy OP
Artful Bodger
 
Joined: Oct 2006
Location: Coventry, UK
Oddometer: 3
ok ive found a second hand barrel and matching piston.

is there much work involved in getting the engine and rear wheel section off the chassis?

all i can see that holds it is a sorta long bolt for the swing motion and the shock?

i have fairly good mechanics skills (on a college course on light vehicle repairs) so should i find this a hard job?

thanks for your help so far...
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