Piton hitting the top of the engine where glow plug sits!

Dhilan

Member
Messages
21
I just picked up a .28 for my friend and when I opened it up to inspect it I saw heavy scratching on the top where the glow plug sits. I have turned over the engine with the roto start and can hear the piston or sleeve hitting the head button. Is this engine a write off? Should I even attempt to start it?

Attached pics of damage
 

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Jam 1

Active Member
Messages
110
Location
Lake County California
check the lower end, the bushing in the rod can wear thereby allowing the piston to travel too far upwards , also close up pics of things makes it easier to view....
 

Gazzman

Well-Known Member
Messages
266
Location
Haywards Heath, Untied Kingdom
Not seeing any Head gasket sims, if it's a F4.6 should have 4 x 0.2mm sims between the head and block. If it's a K4.6 then it should have 2 shims, 1 being 0.15mm and the other being 0.3mm. If these are missing then this could cause this issue. Another cause could be a knackered conrod, IE the big end brass bush worn.
Only 2 reasons this will happen.
 

Dhilan

Member
Messages
21
Would you guys say this engine is worth saving or is it too far gone. There is also a black rubbing mark inside the sleeve
 

Gazzman

Well-Known Member
Messages
266
Location
Haywards Heath, Untied Kingdom
Pop the backplate off the mill and check to see if there is any play between the big-end on the conrod and the pin on the crank. There maybe a small amount but if it is excessive then it looks like the mill needs a new conrod and maybe a new crank, usaully only a rod. If its an F series then worth replacing but if a K series parts are discontinued and cost an arm and a leg if you can find them.
 

Dhilan

Member
Messages
21
It’s an F series thanks for the help I will decide if I’m willing to spend
 

Gazzman

Well-Known Member
Messages
266
Location
Haywards Heath, Untied Kingdom
Been looking at those photos of the under head, the piston hitting the head would not cause that sort of damage, There must of been metal fagments in the combustion chamber to cause that sort of damage. Maybe the bearing cage on the crankshaft inner bearing has broken up but whatever caused it, think you would need a new underhead. Would defo end up being cheaper to but a new F4.6 mill. Got a new Force 4.6 the other month off eBay complete with carb & pullstart for £105

https://www.ebay.co.uk/itm/354161602500?ViewItem=&item=354161602500

This is the exact same mill as the HPI F4.6, all parts are interchangeable.
 
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