1978 1200 Barely cranks

triumphguy

triumphguy

Junior member
Good evening all,
I am finishing up the refurbishment of this 1978 1200 I got off ebay a few years ago.  Since the cylinder needed to bored anyway (62,000 miles) I bought Ross hi-comp pistons and Axtell cams.  Everything else in the bottom end looked good although I did not disassemble it.
I have hooked up most of the electrical system so I'm checking everything and I find the engine will barely crank over with the plugs in.    On the bike's battery (new 30AH) it will barely make one revolution.  This is with new 4ga welding cables from the battery to the relay and relay to starter.  I put in the starter from the Laverda street rod and it acts exactly the same. With a good car battery hooked up directly to the starter (bypassing the relay) it turns very slowly, maybe four or five revolutions, then stops (the cable by this time is quite hot).  Going directly to the starter terminal makes no difference.  With the plugs out it spins merrily. 
I measured the compression ratio at 10.4 to one prior to assembly.  Cranking compression with throttles wide open is 135 psi on all three cylinders.  As I think about it I recall that the pin location on the Ross pistons was different from stock but I don't recall if it was higher or lower.  The flat part of the crown on the Ross pistons was even with the top of the cylinder so I didn't worry about it.  I'm not getting any mechanical contact and no strange noises.  I have a hard time believing that these pistons have such high compression that the engine won't crank over with a new battery, new cables and good starter and relay -- but that's exactly what is acts like. 
I have a spare cylinder and stock pistons and A11 cams which I will install if I can't find another answer.  I am so close to finishing I just want to get it it done and ride!  Any suggestions appreciated.
Thanks,
Patrick Cherry
Ojai, CA  USA
 
Hi Patrick,
Great to see another Laverda is saved.

It is not your pistons at fault, look at attached photo.
Shows a Ross Hi comp piston on the left, dirty old standard Mondial on the right, our Ross very high compression 83.0mm piston in the middle.
Note they are all line up on the gudgeon pin hole.

On the race engines we are building for Oz Laverda, the Ross pistoms protrude from the barrels by about 3/16".
Don't have any trouble firing those engines up though we are using a remote starter.
On my No 2 Jota, 81 Jota with everything, she is running 82.0mm Ross pistons at 11.2:1 compression, starter struggles sometimes but in general spins over okay.
Her main problem is the sprag clutch, sometimes has trouble gripping.

I'd suggest you grab the starter motor from your street rod and give that a try.
If that does not work then you must have the timing wrong somehow.

HTH
Red
 

Attachments

  • Hi comp Piston 2.jpg
    Hi comp Piston 2.jpg
    171.8 KB · Views: 45
Shit Patrick, I've just had my barrels bored for 81mm H/C Ross pistons and I also run Axtell cams. The new battery I just brough was the smaller option Deka 14 and I've made a battery box out of carbon fibre that doesn't allow the fitment of a larger battery so now you have me worried. Once I reassemble I plan to give the starter a good service and fit fresh cables. I'd be well pissed off if the motor didn't crank over with my smaller battery, don't fancy making another battery box as I've already scrapped the first finished one to make a MK2 version 50mm wider so I could fit all the electrics/ignition and a tool roll into it. I'll follow this thread with interest, hope your problem is something simple like a bad earth, good luck
 
Hi Patrick,
Sounds like very nice work you have done.

I had same problem attempting to commission my Jota after finishing the build. I even went out and bought a new battery...same problem.

The cause ( and in hindsight this is embarrassing ) The engine oil level was too high. This is a very bad thing to do but I lucklly didn't do any damage at all. The high oil level causes an increase in crankcase pressure and  et voila the problem of sluggish cranking. High oil level is worse than low as along with this problem the high oil level is picked up by the crank and the oil is whipped up into a froth. Froth = oil + air. Air is not good at lubricating and damage can be done to your engine.
Our bikes have small oil capacity compared to auto and therefore just a little extra can cause a problem.

The other area I would look at if your oil level is between high and low mark is the crankcase breather valve ( ball ) . Is it stuck ? I have not had this issue but I can imagine it could cause cranking problems.

The other area is electrical ( as pointed out to me at Scampton Uk by Clem ; ) is that the brushes on the starter motor may well be worn as they may be the originals.

I hope you solve your problem but please look for the simple solutions 1st ; )

atb

joe
uk
 

Attachments

  • P7270162 (1).JPG
    P7270162 (1).JPG
    185 KB · Views: 34
3C_Stefan said:
I would recommend a starter overhaul, mine has shown serious wear on collector/brushes and lots of dirt inside at around 70k miles on the engine. Took the starter apart, worked the collector over on a lathe with sharp tool by cutting stepwise only slight amount of material off it until it?s even, clearing the slots afterwards. Then soldered new brushes by using min. 60W solder iron, acid free solder and avoiding copper wires soak the solder tin too far into them.
Checked the bearing bushes too and found them in good condition, but in case they are easily changed and cheap. Spent a new seal, some fresh paint on the starter housing. Took me 3 hours and 25$ and the starter works/looks like a new one.

Avoid testing the starter laying on the workbench, it will probably have a take off for nice flight trough your workshop. Don?t even think about testing the starter holding it in your hand. :o

Keep on riding,
Stefan
Click to expand...

Nice write up Stefan
joe
 
Hi Stefan,
Where did you get the new brushes from. ?
I have a few Starters at home I need to repair.
Are they common to anything else ?


Red
 
As far as I know, if it is a Bosch starter (not the RGS/Jotas SJCE), they should be readily available. OCT has done some repairs, friend of mine who used to be a Laverda rider, too, has a shop for building and repairing electric engines, he overhauled my starter roughly 10 years ago. Never had an issue ever since.
 
I've juste heard that there was a mistake done recently by Ross on a small batch of pistons made for Laverda, the pin location is slightly offset so the piston protudes too much. Ask to Wolfgang, he might be able to give you some information.
 
Good evening,
I just returned from helping a friend bring home a Messerschmitt KR175 to find all these suggestions!  I am definitely going to try the starter overhaul.  The starter from the Laverda street rod cranks slightly faster but not enough to matter.  I have no idea how many miles that engine has.  I don't have the coils hooked up so the ignition timing is not an issue.  I have the ground (also 4ga) going from the right rear engine mounting bolt to the neg terminal.
Red, as I looked at your pictures I think it was the top ring position that was different on the Ross pistons, not the pin height.  I think I would have written it down if the pin position was different (at least, I would like to think I would) and my notes say nothing.
I put three quarts of oil in it -- I don't know if that's enough to make a difference in cranking.  I am getting oil out the left crankcase fitting for the cooler as it cranks.
I am not yet to the point that this is the last thing keeping me from riding it so I will tend to the starter and report back.
Thanks once again,
Patrick Cherry
Ojai, CA  USA
 
Pat,  what happens if you try to turn the crank over manually with a socket on the end of the crank nut, can you do it.  First try doing it with the plugs out should be easy to spin and you can listen for anything unusual then try it putting one plug in at a time....
    I remember one time a while back I could not get my Lav to turn over so I hooked the starter up directly to my Toyotas battery with the biggest jumper cables I had,  started the Toyota then made the final connection to the starter and it spun it up fine.
    Could be the starter has a lot of grunge build up increasing the resistance a good clean might be the ticket.  I got brushes from Scott Potter a few years back.
                                                Cheers Dave.
 
3C_Stefan said:
jotajoe said:
If anybody has a worn out set of brushes I could send them off to Motorworks and ask if are common to old Beemer brushes ?

joe
Click to expand...

Joe, unfortunately the brushes of the beemer 2V flat twins didn?t match, but a good hint to try it elsewhere. In motorcycle application me knows only about Guzzi 750S/V7 Sport using these brushes in their OEM Bosch starters. Bosch part nr. of the brush set is 2007014027, this may help sourcing them. In US e.g. www.engelandmoto.com offers these brushes as NOS parts (search their website for the Bosch number), but don?t know if/how much they have actually in stock.

As far as i know Bosch delivered starter series using these brushes also for smaller marine engine applications, so next to nothing the engine workshop at the marina maybe worth a try.

Keep on riding,
Stefan
Click to expand...

Thank you Stefan,

You are very helpful and informative..Appreciated

joe
 
You must log in or register to reply here.
Back
Top