750 strip

I will be fitting some better oil pipe Mark. The old stuff was very thick walled. Seeing as the oil filter is mounted on the gearbox cradle I'm considering metal pipe for the return line with a small length of rubber to allow minimum flex.

The bores are in fact shot. A previous hone had taken them out by 0.002" and on top of that there is a further 0.012" of wear. I may be lucky to get a +0.020" rebore to clean up. (The man I've been recommended for reboring says he has a pair of +0.030" pistons with domed tops. sounds very odd to me but I'll have a look.) In addition the top face to base is out of parallel, there is a run out of 0.006" front to rear. I believe that the original bores were bored square to the base face so plan on getting the top face skimmed.

Swinging arm pin is worn by 0.002" I think there is more wear on the pin than the bushes.

Wish I'd cleaned the bike better before I started stripping it, parts washer is working overtime.

I had drained the oil tank after a run prior to the stripdown. Thinking that all the oil (or most of it) would be in the tank, when the sump plug came off another 300ml dropped out and when manoeuvring the engine to get it out a further 50ml was liberated. Some of this would have been in the cavities of the crank and some drained down from the head. My oil changes in future will always include the sump plug as 350ml of old oil mixed with the new, defeats the object a little.

The rear frame loop should, according to the diagram in the w/shop manual, be parallel to the bottom frame rails. mine has been bent up aft of the top suspension mounts by about 5 degrees. It's only taken 37 years of ownership to notice that. It looks nicely symmetrical almost as if it'e been done deliberately. I might leave it. Anybody else seen this "mod"? I know that normally they are bent down under the weight of pillion/luggage.

Levelling the rear iso bolt on a piece of granite worksurface reveals a 0.015 runout on the front iso bolt left to right in the vertical plane, and the front mounting holes are 1mm further away from the rear iso bolt on the right and 2mm on the left. (I have always struggled to get the front iso bolt in) Out with the rat tailed file and mig welder. Just need to check perpendicularity of the rear iso mount to the steering head before committing myself to removing metal.

The joys of Commando ownership!

Well, since march, much has changed. I spent considerable time and energy trying to get the frame holes perpendicular to the headstock. I reinforced the top damper mounting brackets and welded two lugs to fit my Craven rack without unsightly clamps spoiling my powder coating. I've rebuilt the engine with a PW3 cam and discovered that just fitting it with the standard timing results in a cam advanced by exactly 5 degrees (crank) that took some mental gymnastics to retard the cam but I reversed the technique John Hudson outlined in his tuning notes to advance the cam timing. Success.

Re-assembly easy with nice clean shiny components, engine in gearbox in forks on, wheels on, check the wheel alignment. Nowhere near. Bo---cks. Much scratching of head and ............tear it all down again. To cut a long story short, the headstock is twisted anti clockwise when viewed from the front, meaning that the wheels are not parallel in the vertical plane. A 25mm dia rod through the steering bearings is 7.5mm to the left of the frame centre line at front iso bolt level. By the time that gets down to the bottom of the front wheel rim the error is 12 mm! to straighten the headstock is in my opinion not feasable. there are no signs of damage or bent tubes so I have an immaculate shiny frame that is good for nothing. Having done all the good mods and spent £100 on powder coating I was loosing the will to live. I always wondered why I could not get the wheels to line up without skewing the rear wheel in the swinging arm, now I know.

Read next weeks exciting episode.

Everything is back together and last weekend I borrowed a pair of race rollers to get the oil circulated. That saved me an awful lot of kicking. Yesterday, final checks done, petrol on and spun it over on the rollers with the plugs out, plugs in, try and kick it into life, 3rd kick it fired (once) onto the rollers and hey presto away she goes. Pushed it off the rollers, let it run for a few minutes, feeling well chuffed with myself, cut the engine, thinking it was on the stand, let go, Crash down she goes. to quote Victor Meldrew "I don't believe it" reinforced with some of the worst language the neighbours have ever heard. Anyway, I never did like those handlebars or that front brake lever.

Without wanting to seem like an advert. The Jim Schmitt carb conversion took up exactly where it left off 10 months ago. Rock solid tickover and no hesitation coming off the stops. Probably the best money I've spent on the Commando. (And boy have I spent some money over the last 37 years?)

Hi Mac,

Re the twisted frame, I spoke to Martin Russell who used to be a frame maker with BSA I believe. When I described the problem he advised me that the frame would have been "parallelogramed" to one side below the spine and that would make sense. The front mounting bolt never went through without having to apply some leverage to the front iso. Despite following the "worlds straightest Commando" method, the frame needed some serious straightening. Martin said he could do it but my new powder coating would have to suffer with the heating required. One of my Shropshire branch members had a brand new frame supplied for an insurance job and it was correct for the year. The old frame is in the "pending" tray.

JSmotorsport.com will take you to Jim Schmidt's website He sells some good stuff and he has spent some considerable time getting these PWK flatslide carbs to work on Commandos. They are a copy of a Kehin carb and the kit comes with manifolds, air filters and lower cables. The manifolds are not the best and were supplied to him indirectly by Quaife. He sent me some better ones after the first pair were porous. They work very well straight out of the box and the annoying hesitation coming of the throttle stop with the twin Amal is history. The price is comparable with 2 new Amals but the catch is £75 import duty. Without wanting to defraud the exchequer, if you were going to the USA on holiday you could spread them around your luggage after having them delivered to your hotel.

Search for them on the access norton website. He does a single carb kit as well now. With regards to your single Mk1 Amal I don't think they are up to the job at 32mm at much above 4000rpm

Martin Russell said that heat would be needed to avoid stress building up during the straightening process. He seemed to know what he was talking about and has some considerable pedigree.

Back to the Camshaft timing issue. The bike has been back on the road for about a month and I've covered about 250 miles. She starts and runs well and the exhaust note is crisp and raspy. Whilst I have only briefly taken the revs up to 5000 as part of my breaking in process, the acceleration is not that impressive. Lots of noise but not much go. I was expecting a marked improvement over the pre strip-down standard. (that was with a broken top ring on each piston and 0.012" wear on the bores and the original std cam) I was meticulous in setting the cam timing to achieve 0.145" lift at TDC as per the instruction sheet and, as previously mentioned, that involved retarding the cam by 5 degrees over the standard timing marks. With the std timing marks I had 0.165" lift at TDC i.e. cam is opening too early = advanced.

The $50,000 question is, should I advance the cam to standard timing mark settings to try and improve the performance? there is no kick in the pants as you open it up and that seems to echo what Keith says. There must be a good few members with PW3 cams fitted. I would appreciate any feedback on your experiences. The carbs are Jim Schmidt flatslides and are as fitted before the rebuild and were good then, Ignition is Boyer and set to 31degrees BTDC at 5000.

I posted a similar thread on the Access Norton forum and it generated about 50+ replies. While towards the latter ones, the subject had got lost to some extent there was a lot of good information but I have had no feedback from home i.e. UK based owners. My plan is to advance the cam by 5 degrees, setting it to the standard timing figures. I would appear that Mick Hemmings advocates dialling the cam in as I did, yet Norman White says just fit it as you would a standard cam. I'm beginning to favour that line. Once I return from the French rally, I'll get on with it and let you know my findings. That's if I don't drown