new dude with a 72 comando combat interstate

hi, i just picket up an interstate comando. its a basket case and has been since 1979. im 99% sure i have 99% of the parts. a few known issues are the cylinder head; back in 78 some bad machine work left a hole in an intake port. i'd like to find a replacement head. I'm also missing part of the air cleaner.

if you folks are interested i'll post some pics. it's just a pile in my garage right now.

i'm thinking i'll just build it up with little to no "restoration", keeping the patina. i'll make sure it functions properly but wont mess with any paint of chrome.

i know most of the bikes history. it was only on the road for 7 years. it was torn down for a rebuild that never happened in 1979. it sat in the atic of my stepfather's auto shop for decades. i showed som interest, so now its mine.

i'll be asking some questions around here as i progress through the project. i'm fairly mechanical but this is my first classic brit bike.

Hey ho m.w., you got what I think is the peak cream of the crop of Commandos, both in what it can do and feel like for so far and long, and how long and far it can take you to get it road worthy even if not show worthy. Check forum for sale area, ebay and look in tech section and go down the list of venders World Wide
to stumble on a deal. The most powerful fastest scariest set up I had on my IS Combat was with a plane Jane earlier small port head leaving the miss match of 32 mm maniold lips entering 28 mm head openings. I did leave out base gasket to up CR a bit and a flame ring which is thinner than copper. 2S cam likes a bit of hi CR.
In other words don't sweat not finding a '72 CHO, as they are well know to be over ported for best low down response and I found didn't really help till over 6800, which I would not do much unless upgraded steel flywheel. Its very very hard not to wipe off parts to access and handle, then harder not to wipe even harder once in hand, then about impossible to resist uncovering more and more of the shine comming through, so best wishes getting a good rat patina like my ride buddy's merely power washed '71.

thanks for the feedback.

i dont know what a 2s cam is.

i generaly prefer low end torque so i'll see what i can do to achieve the best out of what i have. i have a pile of recipts to go through. there may have been some other mods done to the motor. i htink it's either been bored out and/or lighter pistons were installed.

the hole in the head is in the intake port. its only exposed to 20 in/hg so i may be able to make do with a blob of jb weld untill i get a better idea of how i want to alter or replace the parts i have.

double S or 2S camshaft has .390 lift intake and .342 lift on exhaust compared to the standard Commando camshaft with .330 lift intake and exhaust. It's what makes the combat engine rev so much easier than the standard 750 Commando. If you have a '72 Interstate it likely as the combat engine provided the engine number is lower than 220xxx. The combat engine is not the engine for somone looking for low end torque compared to any other Commando as it sacrifices low end for more high end horsepower. If you really want to de-tune the engine to standard, you can switch to the earlier head that Hobot mentioned and switch to a standard camshaft. Let me know on the camshaft as I have a standard I would trade for a combat.

Sounds like what ya want is an 850.

monkey wrench said:

if you folks are interested i'll post some pics..

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This. No such thing as too many pictures. Seriously.

And welcome!

Snorton74 said:

Sounds like what ya want is an 850.

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nah. i'm good with what i have. i'll make it work as best as i can. if it lacks low end grunt, then so be it.

i have been reading some scary stuff about the combat motors. ie: massive crank stress. i'll spend more time investigating what upgrades were done to the motor. it has had several things done in a machine shop. i thought it was strange that a bike with so few years under its belt had been to the machine shop 3 or more times. now i have an idea why.

Hehe look at the dyno charts or just go by feel, Combat's don't lack for low down grunt, mine are easy the equivalent of standard cam motors, but where standards aren't worth hanging onto before shifting up, a Combat sure it. Was just taking it real easy today commuting no WOT or even over 70 mph, but had to double check my sense of easy throttle while short shifting d/t the strain I was feeling in my pants and seat lagging behind the eagerness in lower rpms. Sheeze, Ride a real Combat or a standard on loose stuff and get back to me on which has more shit and get it response to watch out for.

monkey wrench said:

the hole in the head is in the intake port. its only exposed to 20 in/hg so i may be able to make do with a blob of jb weld untill i get a better idea of how i want to alter or replace the parts i have.

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Casting voids (holes) are sort of common, sad to say, and are repairable to some extent.
When you get the pictures going, focus (so to speak) on this issuse.
My new old head had a small in the spring seat. Sealed it with JB. No real issue in this area.

More photos.

How many smiles are on the speedometer ?

If you MUST ride in town or observe the speed limits , a standard cam will tame it .

Early ones were ' coustomer development ' machines . :lol: :cry: true entusiasts bikes . :lol:

If its not used for commuteing , the SS cam is o.k. , like a 275 GTB4 Ferrai is ok , but not for fire lanes .

The cam it has will be fine if the lobes are not scarred or badly worn. You'll get used to it.

There are ways to apply modern epoxies to any serious intrusions in the head to make it useable.

Welcome to the forum, you'll find all the help you need here.

(pix, please)

The 850s are notorious for the low end grunt, but that doesn't mean the 750 or the Combat are slouches. Read up on Combat issues. Oiling, pistons, bearings are three that come to mind. I would post photos of your head and get our resident surgeon, Comnoz to to take a look at it. Might as well post photos of the cam too. It is possible (wallet dependent) that you would be happier buying a brand new Fullauto head and building the bike with a newer cam profile that would provide good street ranges. I am not the expert on that but there are plenty here who are.

Welcome on board.
Russ

here are a few pics I took.

this is the pile.



here is the cylinder head. the small "wart" in there is a bad weld or something used to plug the hole the machinist made. there is some blue silicone on the outside that looks like a cookie monster turd.

I do believe a good 850 might out pull even a Combat, for a bit, in the initial parts of each up shift but would be left behind as Combat keep getting stronger so way worth while staying in low gear advantage longer-further-faster. If you are using full Norton torque in stop and go traffic conditions you are nutz'r than me. I ride fairly slow fairly often in steeps in top gear and each time pleased Combat is good form 30 to top out so feels a lot like my wife's auto matic shifing scooter. One way to measure how good the down low response is, is climbing a steep loose slope over 30' loaded down and giving hi throttle to keep going but still barely off idle but any more it don't stall is spins out uselessly. Done on the level unloaded tends to put strain wrists and mash seat.

If ya want low end torque put on smaller carbs, say 30 mm, or even just one, then put on longer headers and the cross over tube or a 2>1, fit non over lapping cam and advance degree the cam till happy as a hog nosing up roots under the out house and about as fast on the fly. An accelerator pump carb would also please ya for the instant hi torque hits.

its been 18 months but i've completed some other projects and can get to the norton again. after sorting out the cylinder head (heli-arced) i'm moving on to unstucking the motor. atf and kerosene. i'll give it a week or two and then il'l start thinking of applying some heat.



its a bit of a challenge as i'm not the one who disassembled this motorcycle in the late 70s. nor have i ever owned a Norton.

Yuk on facing serious tough stuff right out the box but funny clever way to see engine propped up naked in cradle on center stand. Need parts book to go down part lists and decide to stick with factory numbers or jump fence. May consider making a case/crank splitter to put some pressure to part seam if not breaking free at first few attempts. Manual says ya just rap case lip with a rubber mallet and voila on with the show.

hobot said:

funny clever way to see engine propped up naked in cradle on center stand.

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thanks. it took a bit of fishing around in coffee cans to find the "right" bolts. if not obvious from picture, i'm trying to use kick-starter to break it free. i'll try a few whacks with a rubber mallet in a few days.

i'm trying to assemble it with the parts i have. i'd like to keep all the scrapes and imperfections for now as well. i'll likely give it a thorough cleaning and make sure all the mechanicals work properly. i'm sure many surprises await me but i'd like to get it running well before i start going off into the weeds with modifications and such. i really don't even know what i've got yet so just getting it to run may be quite a task.

monkey wrench said:

Snorton74 said:

Sounds like what ya want is an 850.

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nah. i'm good with what i have. i'll make it work as best as i can. if it lacks low end grunt, then so be it.

i have been reading some scary stuff about the combat motors. ie: massive crank stress. i'll spend more time investigating what upgrades were done to the motor. it has had several things done in a machine shop. i thought it was strange that a bike with so few years under its belt had been to the machine shop 3 or more times. now i have an idea why.

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Now you sound like one of us combat owners. Couldn't agree more with the sentiment.

I've experienced the lack of low end grunt on my 2 Combats vs 850's which will pull harder starting a pass but too soon run out of pull so Combat has to zoom around it too for some clear road to keep feeling its easger bullding pull so more dangerous than an 850 in that regard. I also know a well ridden 850 in tights can keep a Combat hard on the boil to keep up and only pass after a while in long open. Its rare someone wants a Commando and a Combat at kept in factory kit with life's hard knocks left intact. I saltue that attitude but also know it don't don't take much blemishes for them to look so down trodden long in tooth obsolete clunkers, so best wishes to stop once the outter grime is off. I saw a old brit single dug out of mud of ditch soaked in Strongarm that freed it nicely on display with UGLY before photos so got some myself and very pleased on its claims and other uses you have to follow up yourself. Weakest component is the mechanical adv unit so may not be able to recover the points ignition to idle back unless able and willing to restore AAU with enough parts I've on hand. Other factory quirk is they took .040" off head but not the pushrods so geometry not idea but they run fine up there a long time anyway. Internal oil passage can get clogged then its front location also blamed for hi rpm wet sump that makes a mess but doesn't skip a power beat so easy trick is plug front hole and open new one over the TS case passage. That and a PCV of your choice in breather hose seals mine to over red line thrills so fasteners rust before oil coats. Othter than that pretty much same as other models main guts. May have to rebore/new pistons but rods, crank, TS drive cogs - pump dang robust easy to restore. Cam and lifters may be shot by wear or corrosion. Tag useageicon after a scan of this. strongarmbrand.com/SitePages/Bikers/WinksTriumph/