B1 Cylinder Head - Pocket Bike Forum - Mini Bikes
 
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post #1 of 15 (permalink) Old 12-04-2019 Thread Starter
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B1 Cylinder Head

Hello
I pulled out a M4 8mm screw out of the hole in the cylinder head
I thought it would release the dome underneath i think its called, but it doesnt do anything?
Whats the reason for the screw/hole? 🤷‍♂️
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post #2 of 15 (permalink) Old 12-05-2019
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Re: B1 Cylinder Head

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Originally Posted by Maird79 View Post
Hello
I pulled out a M4 8mm screw out of the hole in the cylinder head
I thought it would release the dome underneath i think its called, but it doesnt do anything?
Whats the reason for the screw/hole? 🤷‍♂️
The dome presses out with a lil WD-40 and some pressure...Theres an o-ring that makes the seal...

The screw on top is used to bleed the trapped air pocket out of the headcap after the radiator is filled .....

You crack the screw fill the rad and when water leaks out instead of air tighten the screw....

Trapped air causes steam..Steam makes a lot of pressure;-more pressure than your head gasket can take and will make it go pop....

Good Luck

Last edited by CAM2; 12-05-2019 at 02:56 AM.
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post #3 of 15 (permalink) Old 12-05-2019 Thread Starter
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That makes sense thanks, just made me wonder why mine had this screw and other/new cylinder heads didn't.
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post #4 of 15 (permalink) Old 12-05-2019 Thread Starter
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I should have said because you cant see from the pictures is that the hole is threaded for the first 4mm then threaded for the last 4mm then it has a floor, your reply is totaly right about letting air escape etc. No coolant would be able to escape from the hole even with the screw out. I thought it must be to secure the dome but even with the screw out the dome will not budge it seems its all one piece. To be honest i think this particular engine is an older b1 because ive seen those domes unattached from the head and it shouldnt be difficult to remove but this one seems resilient.
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post #5 of 15 (permalink) Old 12-05-2019
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Quote:
Originally Posted by Maird79 View Post
Hello
I pulled out a M4 8mm screw out of the hole in the cylinder head
I thought it would release the dome underneath i think its called, but it doesnt do anything?
Whats the reason for the screw/hole? 🤷‍♂️
That don't look like a Blata head, it looks like a replica head where dome and head are two pieces.

Get your kick with 2 stroke mix
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post #6 of 15 (permalink) Old 12-05-2019 Thread Starter
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Its definitely replica
Where you screw the spark plug in is all one piece its not going to push through. And taking the screw out hasn't released the dome 🤷‍♂️
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post #7 of 15 (permalink) Old 12-05-2019
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probley to bleed air out of the cooling system maybe they failed to get it down into the water jacket those clone engines are known to be extra special...

Faster then a speeding E Revo
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post #8 of 15 (permalink) Old 12-05-2019
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Re: B1 Cylinder Head

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Its definitely replica
Where you screw the spark plug in is all one piece its not going to push through. And taking the screw out hasn't released the dome 🤷‍♂️
You have lots of oxidation locking the o-ring inside....soak the dome in diesel fuel for an hour and with a deadblow hammer hit the sparkplug boss and the dome will release....
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post #9 of 15 (permalink) Old 12-05-2019 Thread Starter
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Good idea 👨‍🔧 thanks
Diesel fuel is that just petrol. Or is it actually diesel i would soak it in
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post #10 of 15 (permalink) Old 12-08-2019 Thread Starter
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Update - the screw secures the dome
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Re: B1 Cylinder Head

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Update - the screw secures the dome
Nice...... ...


Ive built a few Blata rep engines for 7-8ft r/c boats and all of the reps I built didn't even have a hole.....

The dome simply pressed-in as you can see from the picture below..

Judging by the oxidation aswell as rust inside that aluminum-magnesium dome that bike will probably need a whole waterpump rebuild with WP shaft and all.....

Good Luck


Last edited by CAM2; 12-08-2019 at 08:41 AM.
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post #12 of 15 (permalink) Old 12-25-2019 Thread Starter
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Thanks
Your right the previous owner left the coolant in the system. I havnt been able to split the engine to have a look at everything else because the nut on the magneto/pullstart side isnt loosening, do you know if its reversed thread?
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Quote:
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Thanks
Your right the previous owner left the coolant in the system. I havnt been able to split the engine to have a look at everything else because the nut on the magneto/pullstart side isnt loosening, do you know if its reversed thread?
it's a normal thread, you can use a piston stoper or a clutch stoper, heat up the nut will help to loose it.

Get your kick with 2 stroke mix
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Re: B1 Cylinder Head

They sell stuff for loosening threaded bolts and holes & nuts. Liquid Wrench, etc. If all else fails, you can use a nut splitter, after that get a new nut and clean up the crank threads. The flywheel is on a taper, so its not going to pop off, most have 2 threaded holes and you run 2 bolt thru to the cases and force it off. You can remove the clutch housing and put a socket or..... to hold the crank from turning when you try to take the nut off. I have an air gun and Kawasaki electric wheel nut remover, I keep in my truck/SUV. Make sure its on off and hit it, always works for me.
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Re: B1 Cylinder Head

I use an impact gun..They make ones that work with a hammer....

Hit the nut with heat and WD-40..

For engines like the condition of yours I give the whole engine less coil a good soak in a bucket of diesel fuel for a day....

Like Christi stated it's lefty loosey rightey tightey....
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Last edited by CAM2; 12-25-2019 at 05:20 PM.
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