Heart Transplant

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CanukNortonNut said:
I love children! They are surely there to make you wait. Hold on a minuet. All in good time. Merry Christmas to you and your family. God bless
t
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Maybe you guys will realize why I can go full blown restorations of every motor I run across... kids are sucking up too much of the disposable income. My goal is just to get a running bike, not a hot rod that will last 100,000 miles.
 
swooshdave said:
Maybe you guys will realize why I can go full blown restorations of every motor I run across... kids are sucking up too much of the disposable income. My goal is just to get a running bike, not a hot rod that will last 100,000 miles.
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I can relate to that Dave, but watching my kids grow up was worth every penny. I just thought after they were on their own and I was retired I would have more to spend. I think the wife gives me just enough to stay somewhat happy. lol
 
As mentioned on the previous page, you’ve got a 2S cam so why not use it? It needs higher CR to work though. Skinny head gasket rings from JS are a low cost and easily reversible compression boost. Would make for a fun motor!

Maybe there’s a sensible middle ground swoosh. Sure you don’t wanna build this temporary motor to be a super duper hot rod money pit. But there’s no real rush either.

If you do a decent job then it will last, and you can really take your time over rebuilding your original motor (I’m 2 1/2 years into my 920 engine build, I’ve got young kids too, so I’m with you fully on this one)!

New bearings in the bottom end, modified oil return, rasied CR and 2S cam will make for a low cost / high fun motor !
 
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Heart Transplant


In case you guys hadn't figured out I'm a measure once, cut twice kinda person. o_O

Heart Transplant


Seems like more meat than I've seen on a Combat head.


Heart Transplant

How much money should I dump in a head like this? Broken fin, etc. Definitely no stamp.

Heart Transplant
 
With meat on the head gasket flange, no C, and small ports, thats def not a Combat head.

In line with your ‘do it on a budget’ thinking, I’d strip and clean everything, assuming not too much wear on the valves, grind ‘em in and re use (do ensure they go back in the same holes though).

I’d leave the broken fin be.

BTW... you need to slot your board, otherwise you’ll not get it out with pistons fitted...
 
swooshdave said:
How much money should I dump in a head like this? Broken fin, etc. Definitely no stamp.
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What is/was the head on the previous motor? You still have that as an option, correct?

Personally, if money weren't the issue, I'd get the fins fixed, as it would bother me to have a bike with broken off fins. It would also bother me to use a 750 head with larger than 30mm intake ports, especially after all the data on the subject of intake flow rates that has been presented here, indicating that the 750 heads with 30mm (28mm?) are some of the best heads for performance that are out there.

Will you be doing all the work yourself? If you're not, I believe Jim Comstock has stated he welds up broken fins; probably does a great job, too.

I have a friend that had a '70 Commando, all stock except for the "32mm" single Mikuni, with a 19 tooth gearbox sprocket. That bike had no trouble pulling redline in all gears, including fourth, and was very quick all over. We didn't know about such things at the time, but I've always believed that bike ran so well because it had one of the 28mm heads on it.




.
 
Fast Eddie said:
With meat on the head gasket flange, no C, and small ports, thats def not a Combat head.

In line with your ‘do it on a budget’ thinking, I’d strip and clean everything, assuming not too much wear on the valves, grind ‘em in and re use (do ensure they go back in the same holes though).

I’d leave the broken fin be.
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+1

I would also do Superblends. That way the engine is just plug and play for the next DPO. LOL.

These seem to be simply due diligence type items, not necessarily perf upgrades. Kinda like new rings n new gaskets...
 
Building the engine from this state on a shoestring is not going to be easy. Money has to go to new pistons and cylinder bore work for starters. I am thinking alike as Fast Eddie on post #84 how I would approach the cheapest solution for the top end and keeping your cam. I would repair the top fin once you pull out all the rockers and valves. Make a pattern from fin # 7 as it is almost the same stick out as the broken fin. Look at all the threads to ensure there are no more gremlins that will put the brakes on this project. If you still have some of that oak board left, then make a tool to get your pistons into the cylinders once the bores are done. Dimensions are: 7" X 4.375" next cut a 2" wide slot parallel with the long end 5.75" deep The slot is not centered so measure one inch up from the 4.375" This tool will fit under your pistons and support them while you offer up the rings into the bores. Ask your buddy if he has piston ring clamps when you get to that stage of build. I will try and post a picture of the tool.
Cheers,
Thomas
 
waiting for my battery to charge up on my digital camera.:rolleyes: haven't used it in a while. I copied mine from the clymer service repair manual on page 50 figure 42.
but you got it.
Heart Transplant


Heart Transplant
 
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gortnipper said:
+1

I would also do Superblends. That way the engine is just plug and play for the next DPO. LOL.

These seem to be simply due diligence type items, not necessarily perf upgrades. Kinda like new rings n new gaskets...
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Heart Transplant


Well, looky here... lightly used Superblends. My brother found these in his stash. Came out of his bike so we know it's low miles. The question is do I save these for this engine or will I need them for the original engine? I suspect that I will need to pull the blown motor sooner than I thought to get a better inventory of just what on that engine is toast.

But I had been hoping the head on the blown engine is fine. I won't know until I get it out and off. The worse that I could think is that the piston slammed into the head when the rod broke.

Also in the mix is that there is yet another Combat in the inventory... the infamous Rusty Gold. I may need to see what that head looks like. I assume it's... wait for it... rusty.
 
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"Well, looky here... lightly used Superblends."

There you go you just saved $150 greenbacks.
Buy 06-3608 gasket kit, crank bolts 06-7120, + 06-4285 con rod shells (hopefully still standard and not worn, but check before purchase) if you need a regrind then that last number is not going to work. If you want to go "frugal", you can just purchase 4 new con rod nuts 06.2486 (some will cringe at this but use red loctite and reuse the conrod bolts) only as a minimum. Spot punch the t/s half of the crank flywheel and the t/s crank cheek before disassembly. Take that crank apart and clean it. Then put it all back together again and that's done. Do the Dynodave mod on the case, then add your lightly used Supers and you now have a good bottom end with all the guess work out and is now solid. Get the cylinder bores measured and if necessary re bored. I think Comstock can recommend some JCC pistons that are cheap (Taiwanese) with his recommendations for circlips for those pistons. When that is all done, look at your various head options which you just laid out.
Cheers,
Thomas
 
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CanukNortonNut said:
"Well, looky here... lightly used Superblends."

There you go you just saved $150 greenbacks.
Buy 06-3608 gasket kit, crank bolts 06-7120, + 06-4285 con rod shells (hopefully still standard and not worn, but check before purchase) if you need a regrind then that last number is not going to work. If you want to go "frugal", you can just purchase 4 new con rod nuts 06.2486 (some will cringe at this but use red loctite and reuse the conrod bolts) only as a minimum. Spot punch the t/s half of the crank flywheel and the t/s crank cheek before disassembly. Take that crank apart and clean it. Then put it all back together again and that's done. Do the Dynodave mod on the case, then add your lightly used Supers and you now have a good bottom end with all the guess work out and is now solid. Get the cylinder bores measured and if necessary re bored. I think Comstock can recommend some JCC pistons that are cheap (Taiwanese) with his recommendations for circlips for those pistons. When that is all done, look at your various head options which you just laid out.
Cheers,
Thomas
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I'm not really tempted to pull the conrods off. They feel way too good to mess with.

I'm also in the camp that the crankcase mods are useful for racing only. I have a set of Combat cases that are already modded but I may save those for something else. I think you mean Old Britts as I can't find anything on the Dynodave site about the mod.

Once I get the blown motor apart I will lay out all my good parts are let you guys pick and choose. :cool:
 
Sorry man but you got it wrong. pm dynodave and ask him why he does not like the mod shown on Old Brits and the INOA tech digest. Do whats best to float your boat.
Have a Merry Christmas
Cheers,
t
 
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