broken cooling fin (updated with pix)

[turtle13]

so my dog ran through the garage the other day and knocked the extra bore i have been patiently porting and matching off of the table, breaking off about a 3/4 sq inch piece off of one of the fins... should i just chalk this broken bore up to practice porting the bore thats on the scoot, or should i try it and risk a soft seize?
i dont have pics of the carnage... but this was the look i received after the incident, its hard to stay mad...

btw if any one needs a slightly ported 4 bolt intake let me know, i may just have one i will sell you, cheap.

[bakaracer]

you should be ok if the fin is chipped.If a large section of fins were gone than I would be worried.

[iggysepia100]

Second that; let me see if I understand the thinking behind your question: because there is a piece of a cooling fin that is missing the temperature in that little area would be greater than in the rest of the jug, therefore creating the chance of a seizure; very unlikely, in my opinion; not only are temperatures around the jug pretty even throughout but I don't think a little broken piece would increase the temp that much.

[turtle13]

its not reaaly that i am too worried about the general temp raise in the begining, but what it could do in the long run. i am expecting this engine to run slightly hotter, being that it will be with raised compression and some port work as well. some of these things will raise temps a little, but once you put those together and then factor in the fact that in my neck of the woods in KC, pretty much all riding is WOT, then it starts to makes me worry...

[turtle13]

here are pics of the damage...

broken fins

IMAG00252.jpg (36.42 KiB) Viewed 4348 times

[veedubh20]

just can weld fin back in.

[bakaracer]

You can also drill holes in the fins so air can pass through the holes too.That way you will have even more surface area's to cool.The racing circuit guys do that on there race cylinders for better cooling.

[Wheelman-111]

Greetings:

This is a rare time where I disagree with Wise VeeDubh. Welding heat can warp the cylinder. If you do it mic the bore for true or re-bore it. This will require an oversize piston.

If it were mine, I'd just run it as is. And send the dog to reform school.

[dem0nk1d]

try drilling into the side of the fin that broke off and jb weld some post on both sides. Then do the same to the other side. Should hold.

[mr pibbs]

I feel responsible for this.

[turtle13]

I feel responsible for this.

Eh, no reason to. its my fault for putting it on the edge of the table and letting my dog run around the garage. i am in the process of doing some porting on it now, and will run it for a while, atleast for testing. i havent made any ports bigger in the cylinder just yet, but have opened the ports up to where they are the same size all the way through as to not restrict flow. the boost port seems like it was extremely restricted from the factory, i opened it up about a mm in all directions, with out actually making the cylinder ports larger.
what amazes me is that there seems to be a bottle neck in every port, just smothing out the transfers, opening up the boost ports and taking the hump out of the top of the exhaust seems like it will provide a sizable gain (even if it is a mph or two...). i am trying to be meticulous in taking equal amounts out of all ports and to not take any off the top or bottom of the ports to affect port timing, but should i widen the transfers and the exhaust a little to allow for some more flow?

[motomech]

What is that, a MB5 cyl.?
It can be run as is, the engineers design plenty of cooling area into an air-cooled cyl.
It could also be welding without any warpage issuses, but it's not necessary.