Cylinder head issue

Bone91

New Member
Hey there,
So i am currently attempting my first rebuild. I purchased a cb250g off gumtree for $150 about 7 years ago with a plan to restore it... low and behold, life got in the way, moved interstate so the bike went into storage at the oldies place. I have recently moved back home so figured id pull it out and tinker away at it, so far i have pulled the engine and done a complete tear down. Everything seems to be in good shape bar a hand full of things, ill post up a few photos as i would like to get some opinions on what you guys would recommend doing with the issues i have come across.



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I am guessing the PO had welded the outside to reinforce the damage on the inside as it is on both sides. Do you think this will be an issue down the track or should i look at replacing the jugs?

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Here i have circled the seat for the cam chain guide, i am guessing the guide came loose at some point and has bounced around causing the damage. My question is, has anyone had this issue an would it be worth having it repaired or should i be looking for a new head?

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Here im guessing the PO has tried to smooth out the pitting on the combustion chamber, now i dont know a great deal about engines in general but the engine isnt going to run evenly if the combustion chambers arent the same size, correct?

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Oh and this, i could be wrong but to me it looks like someone has botch welded the seat back onto the tensioner arm?

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The weld repair on the cylinder head seams fine, I would be concerned about the tensioner mount. I mean luckily heads for the cb360/cb250 are plentiful in ebay.
As for the tensioner that's just what they look like... old Japanese motorcycle welding wasn't what it is today
 
If you want to see a bodged tensioner arm, wait until i get mine out

Steve
 
Bone91 said:
Here im guessing the PO has tried to smooth out the pitting on the combustion chamber, now i dont know a great deal about engines in general but the engine isnt going to run evenly if the combustion chambers arent the same size, correct?

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it looks like it was machined for a squish band? except that the bands are very unequal. weird stuff, I'd get a new head.
 
doc_rot said:
it looks like it was machined for a squish band? except that the bands are very unequal. weird stuff, I'd get a new head.
Its probably a cb360 head they was "repaired"

The 250 heads didnt have the squish. But the 360 ones did
 
MiniatureNinja said:
The weld repair on the cylinder head seams fine, I would be concerned about the tensioner mount. I mean luckily heads for the cb360/cb250 are plentiful in ebay.
As for the tensioner that's just what they look like... old Japanese motorcycle welding wasn't what it is today
Ok so new head it is... when buying the head would you recommend finding one as a whole, so rocker cover included?

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Bone91 said:
Ok so new head it is... when buying the head would you recommend finding one as a whole, so rocker cover included?

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I'd your rocker cover is otherwise undamaged I wouldn't say to get a new one... these engines were prone to cam journal failure and resulted in bad 'bearing' surfaces on the head and rocker covers making the rocker covers far more expensive than they really should be. If you really want a new one, you can look for one from a cb360 too as they are the same where as the heads differ in the combustion chamber between the 360 and 250
 
Ok so a little off topic but say i was to go a big bore kit like Sderbyshire, would one have to have the CC machined for the a larger piston to seat up in the head properly? Reason i ask is if you do, instead of me putting money toward a new head i could put it into that as the head might have to be machined anyways? All id have to do is fork out a little extra cash to have to guide seat repaired

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Would it not be easiest to go for cb360 barrels, pistons and head, or cb389 :)

I have a set of good cb360 pistons you can have for the price of shipping to get you started!

Steve
 
Ok, i can recommend a seller on ebay for gs850 pistons if you do.

He is cruzinimage_uk and was very helpful and the pistons arrived in less than a week from Japan to uk!

Steve
 
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