Author Topic: How hard is it to kickstart a 650 superrocket engine rebuilt with 8.25 pistons  (Read 4119 times)

Offline steve c

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How hard should  a super rocket engine rebuilt with 8.25 to 1 compression ratio pistons be to kick over ?

How tights tight?

I have rebuilt a super rocket engine for my A7 with hepolite high compression pistons 70mm +0.5 or is it 50 thous so first over size?

It is a devil of a thing to kick over. I am 6' 2" and 17 stone and I struggle with it being tight , lighter friends and my wife struggle to turn it over, It has destroyed the new kickstart pawl I fitted ( probably more to do with the quality of modern parts than being superman). This kills me as I have ms that causes much fatigue after 20 attempts.

It?s my first British bike and I have had no help from anyone knowledgeable in reality as most friends who are enthusiasts pay to get them done at high cost and with varying results.

I have now found that I should have fitted 6.5 to 1 compression ratio gold flash pistons, as they suit modern fuels better. I have had the magneto rebuilt twice and it still won?t start from cold easily.
I am certain I have mastered timing now.

The valve stems are worn and I think it this oils the plugs slightly, that and the reduced cranking speed means that the magneto isn?t going fast enough to spark well?

No cash for head at time and was going to do it later.

Is this a likely scenario.

In which case what to do next? As all this stripping and rebuilding wastes the summer to ride it, and I am losing interest with all the effort and no success?

Clutch with new plates and a new sprocket still wont disengage properly, My surflex plates jammed in this basket and I think that it is slightly miss machined so will have to go back to my supplier (who has been very helpful).
The clutch is all new now except for the hub adaptor with the replacement plates slightly dragging
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Offline alanp

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Steve, I know how you feel mate. I've just rebuilt a Rocket Gold Star with 9:1 pistons and with just about everything renewed in the engine and gearbox and it's not easy to kick over. Initially I was dead worried but then I took the plugs out and turned it over a lot to get oil circulated and it was much better. Standing over the bike supporting it on my left leg while trying to kick it is unlikely to be a pleasant experience but on its stand I can put more weight and swing into it and this works. I need now to get a few miles on it to free it up more before Steve McFarlane converts it to electric start and saves my knee joints from further hell. I'd talk to Steve McF. in your situation.
If you're sure about the mag and timing I would look more closely at the carb. But, if it hasn't fired up at all yet you really must try swopping over the plug leads as well. Good luck.
Alan
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Offline steve c

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It has run, and runs beautifully after its been warmed up, it even restarts well.

I have never had a working clutch but I am near to that even though I will probably have to buy a new 4 spring clutch sprocket to replace the  defective one I brought one in December ( british bike dealers dont appear to do returns).

The plugs oil up so I will redo the head.

The new kickstart pawl failed after I would guess 400 to 500 stiff kicks, will its replacement be any more robust, I am rebuilding a vespa  GS 160cc engine and thats pawl the same size as the puny bsa one.

Do I need to drop the compression for the kick start to cope and the mag to spin fast enough, 400lb is too much to bump start ,

The carb was reconditioned by Martin Bratby so should be ok.

I just don't seem to be making progress
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Offline MG

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Hi Steve!

I'm running my A10 on 9:1 and have no problems kickstarting it, even off the main stand.
It mainly is a matter of the right technique, not necessarily pure power. Even my younger brother is able to kickstart it (he's 16 and has maybe 70 kg or so). I have to admit he has some experience with Enduro machines though.


This is the procedure I follow:

Retard ignition first (automatic on mine, probably yours is manual?). Sorry if this is being too obvious, but forgetting it is not the best idea.

Push the kickstart down gently, until you feel the resistance. You are now somewhere before TDC.

Now release the kickstart and allow it to move upwards until being in a horizontal line, or slightly above.

Gently push the kickstart down, just enough to feel the resistance, but not so much as to push it down further. Rest in this postion for a few seconds, thus allowing the pressure in the combustion chamber to reduce a bit through the piston rings. This makes it much easier to kickstart. If you have the pistons down on BDC and stomp on the kickstart lever, you will notice it is significantly harder to get the psitons over the compression stroke.

Now give it a good hard kick, not stomping or jumping on the lever, but swinging it down forcefully with the full weight of your body behind it.


If there's no way the high CR will work for you, there might be a way of reducing it without buying new pistons. There is a chap called Peter Weigelt in Germany who sells CR reduction plates. I've never seen them advertised elsewhere.

However, here's Peter's address and phone number:

British Bikes Weigelt
Alte Darmstädter Str. 22
64521 Groß-Gerau OT Dornheim
Tel.  0049 - (0)6152 98 78 18

Here's the link to the plates: http://www.bb-weigelt.de/pbuchs.htm

The German text basically says:

"As BSA A10 and TRI T120 engines with a CR of 9:1 always tend to ping, we had compression reduction plates manufactured for these models. These plates are made from aluminium and are fitted between the crankcases and the barrels using two gaskets.
Often people don't consider that the CR increases significantly when boring out the barrels. Retarding the ignition to reduce the tendency to ping let's the engine run at higher temperatures, a bad solution, especially for OIF models."


I actually don't know whether Peter speaks English, but I'm pretty sure he does, as he is dealing with brit bikes and spares since years. If not, I might act as interpreter if necessary.

Cheers, Markus
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Makus

That is exactly what I am looking for, however I cannot see an email address. Have you any idea of the cost?

John
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Offline MG

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John,

Sorry, no idea about the price.
AFAIK Peter is only available on the phone, Mo.-Fr. 8 a.m. to 9 p.m. (sic!).
I don't know of any email address, I think he's a rather old-fashioned guy.

Cheers, Markus
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Online chaterlea25

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Hi Steve,
There should be No Problems to starting your bike with 8.3 pistons!!!
Firstly, what oil are you using? straight 40 or 50 will be hard to turn over in cold weather
second, what size primary drive sprocket is fitted?, smaller engine sprocket means harder to kick over (super rocket 21,22,23 teeth???)
Is there some mechanical problem, does it turn over freely with the plugs out?

Is the correct cylinder head fitted?
the part number is on the underside of the inlet manifold,  67-1126 earlier road/super rocket, 67-1549 or 67-1571 late Super Rocket/RGS
I recently had trouble with a "Super Rocket" that came fitted with a 500cc A7SS head!!!!!

HTH
John O R
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Offline muskrat

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G'day Steve,
                 I have no trouble starting my cafe at 10.5 : 1 but it does have tall primary gearing 23/43 making it a little easier. First kick every time hot or cold. I have two blown discs in my back so any more than 5 kicks and I'm buggered. MG's method works for me even when it was tight from rebuild.
Your clutch problem may be related. Do you free the clutch by holding in the lever and giving a few kicks first ? Some say that with the modern plates you don't need to but I do anyway. You should feel no or very little resistance at the kick lever. If you do it's in the kick mechanism, main shaft or clutch.
I know it is frustrating and time consuming finding the cause of problems like this. Just slow methodical inspection and repair of each part in turn.
I don't think you should have to lower your CR but if you do it's easy to make a plate out of alloy sheet. Just use a base gasket as a template. A 1mm plate will drop the CR from 8.5 to 7.75.
Don't give up.
Cheers
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Offline dpaddock

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Do this for us:
Remove the spark plugs, ground their bodies against the engine and swing the starter thru. Two things should happen. One, the engine should rotate easily (even if the kickstart is operated by hand), and two, there should be fat spark at the plugs.
Do this and report back, OK?

David
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If it turns over freely by hand without plugs then mechanically all is well.
I had an A10 with 11.5 : 1 in it , extra heavy valve springs and a really big primary sprocket .
Being not the biggest or heaviest 18 year old I had to resort to things like starting it on one cylinder till it warmed up.
Like yours once hot it started easily.
99 % of my problems were lack of proper technique which eventually I learned.
In my case it was to turn the engine over just past TDC so there was some momentum in the engine before it had to overcome the compression.

It took a long while as the previous bike was a CT 50 Honda where you did not bother with technique.
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As for compression plates.
There is nothing fancy about them.
They are just thicker cylinder base gaskets.
You can cut them your self from aluminium, copper or packing board ( what I use )
Packing board is just thicker, tougher & harder paper and is designed for just what you want to do , packing out two parts. The good bit is that as it has some compression ( not much ) it will make a seal.
Garlock makes it in about 100 different thickness.
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Offline steve c

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Thanks for all the great ideas.

The packing plate idea seems to have value much cheaper than swapping pistons.

It is filled with chatsworth mono grade 40 sae, and a bit of 20/50w, I fitted a cartridge filter.
That could be making it tight. I wonder if 20/50 would be better and less stiff. I am going to change it every 3K anyway.

The mag is a k2f manual. Starting with lever pulled back, about half choke and couple of presses on the tickler.

I will check the feed to the rocker spindles as I cleaned it all out, check I have taken it from the right side and not delivering to much oil, I will check the union bolts have not been opened up again drowning the top end in oil.

The head is the right one with new springs and valves relapped and in good order with exception of the guides, I will check the number

I have the starting technique and I have been rocking to find a compression stroke its just not going quick enough for the mag to burn the oil off the plugs.

It has a big sprocket on the crank. Its much freer with the plugs out but spark is border line on sparking well even at that speed, magneto is good as was the other one.

The kick start pawl failing is bit of a pain as is the clutch dragging, I need to sort those issues

I am sure there is only one manufacturer (MCA) for most of the engine parts so you will struggle where ever you buy them with the poorer quality of later years as english engineering shrinks.

The head is I feel dripping oil from the valve stems which is fouling the plugs and that engine being stiff with the plugs in dropping the cranking speed.

I am not sure how to prove the carb without buying another !

I

Thanks for everyones time and suggestions and the time taken to post them, a few phone calls to make tuesday I think ref clutch and kickstart pawl.

thanks

Steve
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Online Triton Thrasher

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Perhaps you're retarding the spark too far.
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Offline steve c

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Just been having a go at it but the kickstart is not playing ball, took all the bolts and screws out but the front casing doesnt want to split

did try to go with the advance lever pushed further forward got stiffer the more I kicked it

but kick start is slipping had a new bush and gear and pawl, quadrant was ok,
wont come to bits for inspection

just checked its not wet sumping it isnt and hasnt

might be worth trying some thinner oil  20w 50w? its quite stiff even with plugs out and mag is just on the cusp of working really well

steve
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Online chaterlea25

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HI Steve,
Once you sort out the Kickstart issues and are ready to try again,
As TT says perhaps you are retarding too much, only pull the lever back enough to stop the engine kicking back
I find around 1/4 to 1/3 of the way back to be best,
If the valve guides are very worn they will let air and oil into the combustion chamber,further weakening the mixture and making starting harder!!
I cant see (in my mind) why the outer cover wont come away easily???
Leave the kickstart in place and use this as a handle to pull on the case, pivot it back a little, the only other time I have had trouble was when some PO of a bike I was working on had a mishmash on the speedo driving gear (not pretty!!)
HTH
John O R
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