The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: coater87 on 11.04. 2009 05:59

Title: Bottom end problem or ???
Post by: coater87 on 11.04. 2009 05:59
 Hi guys,

 Its been a while since I was able to do anything with my bike, but now that I had a little time I have run into an early problem.

 If you remember, this bike is a 56 GF that was torn apart right after "Easy rider" came out. Well, I honed out the jugs and put in new rings. Checked the ring gap and the normal stuff, and put the head and box on. Everything went together smooth. My plan was to get it running in the rough, see what all needed to be done right off, then tear it back down with a good plan in mind.

 The problem comes down to when I try to kick the bike over, I cannot do it with the plugs seated. I back the plugs off to leaking and it kicks fine. Now the plugs are not hitting, the bore is stock as is the piston, and there are no major rattles when kicked without the plugs and the valve train seams to be working fine.

 Its almost as if I suddenly have 40:1 compression! When the plugs are seated, it will not move at all- with one seated and one out I can barely get it to turn. It honestly feels like I am going to break the kicker off.

 Is it possible my bottom end is that shot, or am I thinking in the wrong direction here? I know I should have wild compression with new rings and hone for a little while, but this is way too much and I am fearful of making a bad problem worse here. Any thoughts?

Title: Re: Bottom end problem or ???
Post by: Brian on 11.04. 2009 11:03
If it kicks over ok without the plugs in and you have the correct reach plugs then it may simply be too much oil in the chamber. Try taking the plugs out and kicking it over several times or even putting it in 3rd or 4th gear and pushing it a few yards. Put the plugs back in and try again and see what happens.
Title: Re: Bottom end problem or ???
Post by: fido on 11.04. 2009 13:51
Are you sure it's not just a problem with the kickstart? They are not the best design known to man and they do tend to lock up.
Title: Re: Bottom end problem or ???
Post by: dpaddock on 11.04. 2009 17:25
If it's too much oil in the chamber, I suppose it would be squirting out the spark plug holes when kicked over without the plugs installed.

Check that you have 1/2" reach spark plugs and NOT the long reach (3/4") plugs.

Title: Re: Bottom end problem or ???
Post by: RichardL on 11.04. 2009 18:23
So, if the pistons start around bottom, with the plugs in, does it let you kick a little and then jamb. If not, I can't see as how it could be the plugs. One thought I had, was that, maybe, if the bearings are dry or damaged, the additional radial force due to the compression might be enough to raise coefficient of friction to a high value. Others, please sing out if this is way off the wall.

Richard L.

Title: Re: Bottom end problem or ???
Post by: coater87 on 11.04. 2009 19:35

 Its not to much oil, that was my first thought and I must have kicked it over 50 times with no plugs- in addition there is no carb or exhaust mounted.

 After reading it might be the gearbox, had a buddy hold a large breaker bar while I kicked it a little. The kicker seams to work fine with no dead spots. Now if that's enough to be sure is unknown yet, but I am really leaning toward a very bad bottom end here.

 But on the other hand, the rods and crank turned smooth with very, very little slop at all. This is the reason I decided to go ahead and try to get the motor running first without breaking the cases.

 I am hoping this doesn't turn out to be like one particular street rod we built. We always built them in the rough first, get them going then decide what needs to be done or changed before we break everything down for painting or plating. Well, with that one every step forward required three steps back to get to where we used to be! :!

 If nobody has any additional thoughts on what this could be, I think I will just plan on having to break the cases and mocking the bike up around a rebuilt motor.

 Now, does anyone know of a good machine shop in the Wisconsin area that can handle BSA stuff? I know they will all say they can, but I would rather go to someone that a member of this board has had good luck with.

Title: Re: Bottom end problem or ???
Post by: dpaddock on 11.04. 2009 19:55
Did you check the plug reach as I suggested?
Title: Re: Bottom end problem or ???
Post by: LJ. on 11.04. 2009 20:05
Lee... Give it a few more days before you dismantle, Other members may come up with ideas when they look in. Sorry I cant give any ideas myself, I'm only thinking here if you might have an A7 head on an A10?? Is that possible guys??  *dunno2*
Title: Re: Bottom end problem or ???
Post by: snowbeard on 11.04. 2009 21:53
wild shot in the dark, did you get the pushrods on the right rockers?  maybe the valves are not opening properly to let any compression out?  cam followers, etc?

I'm a very rank beginner, so my advice should be taken with many grains of salt...  ;)
Title: Re: Bottom end problem or ???
Post by: RichardL on 12.04. 2009 01:07

I think I mentioned these folks to you once before, as they are located in "Very-Close-To-Wisconsin, IL":

Morries Place LLC
(815) 653-7000
5410 Austin Ct, Ringwood, IL 60072

I have not had work done with them, but I have discussed it face-to-face and was impressed by their knowledge. Personally, if I had work to do right now, I would be inclined to trust them with it, myself being in Naperville, IL. Can't hurt to give them a call. Ask them what they think the problem might be. Also, call Gary at SRM in Wales and ask him. This is a big deal and I think you want to explore all the advice you can find, particularly when a known professional shop gives it for free. Think of how satisfying it would be if they both gave the same answer.

Richard L.

Richard L.
Title: Re: Bottom end problem or ???
Post by: coater87 on 12.04. 2009 05:48
 Thank you guys,

 The plugs are correct (1/2 inch) and the valve train is working normally- that's why this is so odd. I am going to take the boards advice here and make some calls before I do anything rash. I will let you all know what I learn or at least what the problem might be. I just have the bad feeling that when under compression load something in the bottom end is binding tight....

 Richard, I remember you had put me onto Morrie's place a while back, I just could not remember the name but I did remember it was pretty close by. Thanks for the reminder!

 Lets hope I am over looking something simple, but I just cant for the life of me think what it may be.

Title: Re: Bottom end problem or ???
Post by: BSA_54A10 on 12.04. 2009 11:30
As it spins quite freely without the plugs and there are no bangs and crashes to be heard but locks up solid with the plugs it really can only be 1 of two things.
Either the plugs are fouling on the piston or valves
the kick start is locking up.

My money is on the latter.
Without the plugs in the only force acting against the kick start is the compression of the valve springs.
With the plugs in there is also compression to overcome.

This extra pressure acting against the kick start quadrant gears causes it to ride up on the drive gear and jamb ( or nearly jamb as the case may be ).

The problem will be a combination of a worn kickstart quadrant &/or bushes ( there are 2 of them )   a worn pinion & ratchet or weak spring, or a worn mainshaft &/or mainshaft bearings.

I have even see this happen when one of  the chains was over tight , causing the mainshaft to move just enough to bind the kick starter .

Even when in good condition ( actually from new with some bikes ) the kick start can bind. The instruction book tells you to engage top gear and rock the bike back & forth to release it .

If you feel the need to verify this then try clutch starting down a hill
Title: Re: Bottom end problem or ???
Post by: beezalex on 13.04. 2009 16:09
It's pretty easy to tell whether it's the kickstart quadrant or not.  When it refuses to turn over, pull the clutch in.  If the kicker then kicks through, the quadrant's o.k. and the problem is in the motor.
Title: Re: Bottom end problem or ???
Post by: trevinoz on 13.04. 2009 23:33
Alex, when mine jams I have to put the bike in gear and rock it. It will not kick with the clutch lever pulled in.
Title: Re: Bottom end problem or ???
Post by: A10Boy on 14.04. 2009 16:40
Why not remove the primary chaincase and chain and see if you can turn the motor over with a C spanner on the cush drive nut, this will isolate engine from the gearbox.

Title: Re: Bottom end problem or ???
Post by: coater87 on 27.05. 2009 00:41
 OKaaay (I guess), I may have found my kicker problem.

 Just popped the head and barrels off this motor. Bore is for sure standard, which is great. Cylinders are do-able as is, which is also super.

 Pistons- look good except for one minor thing. The compression ratio of these has got to be out of this world- I had no idea what road rocket or any other a10 piston should look like until I met you guys, I no longer think these are stock at all.

 But before I go off thinking too much, does anyone have a pic of stock G/F pistons? None of that high test stuff, just cooking pistons.

 These have the normal relief for the valves, problem comes with the dome- and I mean full dome- no flat area in the middle at all. When my buddy raced, these are what we would have called "head fillers", or "valve benders". Also, underneith the oil control rings, are 8 splash oiling holes- really reminds me of the alcohol cars.

 If these are stock or sound like it, someone tell me before I chuck these up in the lathe and make flats out of them! *smile*

Title: Re: Bottom end problem or ???
Post by: RichardL on 27.05. 2009 05:06

I need to be careful quoting years, but if I am readng Roy Bacon's book correctly and if he is, indeed, correct, the full domed pistons will be 9:1 a la '62-'63 Super Rocket, and the same pistons I am running. When you started your description, I thought you were heading to "look like mountain peaks," which would indicate 10:1. My 9:1s are running quite nicely right now, but I don't have enough miles on them or me (really, plenty of miles on me, just not enough of them riding a motorcycle) to judge the ultmate benefit or drawbacks of this somewhat high compression ratio. I've been wanting to post a YouTube video so the sound of these pistons through stock mufflers and with an undertuned cam (356) could be heard/judged by others. I can tell you that the bike has a good deal of pep.

Richard L.
Title: Re: Bottom end problem or ???
Post by: coater87 on 27.05. 2009 11:26

 Thanks for this information, I have a Bacon on the way as we speak. I was a little thrown off by the pics in the Haynes manual showing very flat pistons.

 So the splash oil holes are normal? I also have to check these over for the skirt splits, I dont remember seeing any and its too dark in the shed right now.

 Well, so much for my theory that these may be as high as 12/1 and that is what was causing my kicker problems. If I can get a picture of these, I will post it up for you to look at and see if they look about like yours. They still seam awfully full for 9/1, but then again I didnt even know what stock looked like!

Title: Re: Bottom end problem or ???
Post by: A10Boy on 27.05. 2009 18:36
Its all personal choice of course, but I've heard guys say that with a Gold Flash [with a cast iron head] you don't want HC pistons as the higher compression will produce high temps and can cause pre-ignition. That's why BSA brought in the alloy head to help with heat dissipation on the sports models.

The flat tops produce a 7.25 compression ratio with a cast head and make a very sweet motor.
Title: Re: Bottom end problem or ???
Post by: snowbeard on 27.05. 2009 20:44
I think the oil splash holes are pretty common, at least they are there in my 60 super rocket with +060 pistons, my brand new hepolite +060 pistons, and the old beater +040 pistons I have. 

what came original stock may or may not have them, but it seems in my n=3 that they are supposed to be there ;)
Title: Re: Bottom end problem or ???
Post by: coater87 on 27.05. 2009 21:50
 Thanks guys,

 Andy, I agree about the higher compression, it is certainly nothing I want at this point. I may ask around a bit for a few measured figures on a stock piston- then honestly lathe these off. The "hump" is not hollow, but I do see a few balancing marks, so someone had an idea what they were doing.

 The more I think on it, these pistons may have been the saving grace for this bike. The brothers told me that after the (chopper) "rebuild", the bike never did run correctly, and during trying to figure out what was wrong they gave up on the project.

 Of coarse, this was after they broke every other fin off the head, and drilled 5/16 holes in the rest and threw all the hard to find bits away.

 I figure this is what happend: they added HC pistons to a good running motor, swapped out the smaller carburator for a larger bore/jetting, and added straight pipes. The Mag may have been a little weak so really poor spark now, coupled with flooding and no exhaust back-pressure and that was the end. Lucky me! *smile*