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Andy
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Coastal BC, Canada
Joined: 02/12/2011
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Hi

It's been a long while since I last posted to the forum and in the meantime I bought a blue 1973 R75/5. It is in great shape but has a starting issue that has me foxed and I wondered if anyone else had come across this before.

The bike originally had a Boyer ignition. Looking through the PO receipts in fact it was the second Boyer ignition, the first was assumed to have failed by the PO because the bike was really difficult to start, despite the fact there was a healthy spark at both plugs. Boyer replaced the unit and the same problem persisted.

When I bought the bike it was almost impossible to start and I was advised to replace the Boyer unit with a Dyna III. After fitting the Dyna III I still have the same issue. With plugs removed and grounded, the engine will crank smoothly at high speed. If you install a second set of plugs, and keep the HT caps grounded again, the engine will crank smoothly but with less speed as now both cylinders have compression. If you connect the HT caps to the plugs the engine labors and occasionally graunches to a halt. It seems like it is "dead heading", the plugs are firing at the wrong time in the cycle and igniting residual mixture at some indeterminate point in the firing cycle.... really weird, the starter sounds like it is in great distress, yet with the HT caps off (obviously no spark) it will spin the engine like a champ......

The battery is new, the valve clearances have been set correctly, the bike has 118 psi compression on one side 120 psi on the other. The Dyna III unit is set so the magnetic trigger on the crank nose just turn on a light when the S mark appears in the timing window. With full choke the plugs get pretty wet quite quickly.

I am struggling to think of a reason why the engine will not start, does anyone have any further things I can check.

All and any help gratefully received.

Cheers

Andy

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Andy
Saltspring Island, BC, Canada
1972 R60/5, 1973 R75/5, 1960 R60/2, 1981 Moto Morini 500, 1946 Harley Davidson WL45

wolds
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hard to start

You're on the correct cylinder and on the compression stroke right?

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2007 BMW R1200RT
1979 Yamaha XS650 "cafe"
1976 BMW R90S
1976 BMW R60/6

schrader7032
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San Antonio, TX
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Compression should be closer

Compression should be closer to 150. Your numbers are significantly down...either you measured compression on a cold engine or there are problems with the engine.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

wolds
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valve clearances correct?

valve clearances correct?

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2007 BMW R1200RT
1979 Yamaha XS650 "cafe"
1976 BMW R90S
1976 BMW R60/6

MikeL46
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Since you've checked and

Since you've checked and rechecked everything, are the S and OT marks accurate?

Verify the OT with a tool in the spark plug hole and verify OT is at Top Dead Center. Be careful not to damage the spark plug threads.

Mike

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69 R60/2 76 R90S 78 R100RS
70 Triumph w/Spirit Eagle Sidecar

Andy
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Coastal BC, Canada
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Thanks for the feedback

Thanks for the feedback everyone, just some follow up comments.

The engine compression was taken with a stone cold motor. I haven't been able to start the engine recently at all. Valve clearances are all good. I am sure that I had the correct cylinder on compression when I used the light, but I will check again tonight. Since both plugs fire at the same time (wasted spark?) I am not sure this is crucial but please correct me if I am wrong. The OT mark is indeed TDC so I am assuming the flywheel is correctly installed. Interestingly when I swapped out the Dyna and went back to points I still had the same problem, so it is not Dyna related....

I spoke to Dyna today who confirmed that my installation, as I described it to them, was correct. The suggested that I check all the cabling from the battery to the engine ground and to the starter. They thought that if the starter was laboring then the extra load imposed as the engine tried to fire might be enough to create the "graunch" sound I am hearing.

Two extra things:

The positive terminal of the battery gets noticeably warm after cranking the bike for 30 seconds. There seems to be quite a lot of current draw. Does anyone else notice this? Is there an easy way to measure current draw and if there is what numbers would I expect to see?

I also measured the current at the battery and when cranking see 5v voltage drop, from 13v to 8v or 9v when I hit the starter. Is this about right or more than expected?

Once again appreciate any comments and feedback.... I would love to post a solution!

Cheers

Andy

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Andy
Saltspring Island, BC, Canada
1972 R60/5, 1973 R75/5, 1960 R60/2, 1981 Moto Morini 500, 1946 Harley Davidson WL45

schrader7032
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San Antonio, TX
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You should never see the

You should never see the battery drop to below say 10-11v, so there's clearly something wrong. You say the battery is new, but I would want to know for certain. I bought a new battery for my /7 and it failed on me in a very short period of time...that was a first for me...got a new battery under warranty. So, I'd pull the battery and have it load tested.

If the battery is fine, then likely it would be something in the starter. Bushings could be worn and the armature sticks or runs off center and you get a lot of current draw. In my limited knowledge, either the battery is toast or the starter is.

Does the bike have a kick starter? If so, I presume the bike runs fine when kicked?

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Andy
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Coastal BC, Canada
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Thanks for the reply Kurt.

Thanks for the reply Kurt.

Yes, the battery is new, a 30ah AGM, but I am not discounting that it could have failed fresh out of the box. The thing that makes me slightly suspicious is the case is slightly bulged. I have only ever seen that on lead-acid batteries that have quit on me, can AGM batteries show the same bulging symptoms?

I am going to check the starter connection tonight. I think it is brand new, I have the old one in a pile of spares. I don't know why it was swapped out but the old one shows minimal wear and I am tempted to put it back in and see what happens....

I could try kicking the motor into life. To be honest I have had limited success doing this over the years and am always slightly wary of dropping the pin into the transmission. I will let you know what happens...

Cheers

Andy

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Andy
Saltspring Island, BC, Canada
1972 R60/5, 1973 R75/5, 1960 R60/2, 1981 Moto Morini 500, 1946 Harley Davidson WL45

Twocams
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Never seen a AGM bulge but

Never seen a AGM bulge but that dont mean it cant. Make sure when you buy a new battery that you charge it up. I know they say its charged where you bought it. But they charged it 2 months ago. Try the other starter.

twocams

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69 R69S 03 K1200GT
92 R100RT

sminn560sl
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Central Kentucky
Joined: 04/13/2011
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Starting Problem

Andy, I hesitated to post this because I didn't want to sound negative, but thought it may be helpful in some way.

I had a similar problem with my 74 R90/6. As it's a first year (4/74) model it is quite similar to your /5 (even the same handlebar switches). My bike became increasingly difficult to start. I tried all of the usual remedies, cleaned/adjusted the carbs, checked dwell (points gap), valve lash, timing, etc. Everything seemed dead on as best I could make it. One morning I went out to start it for a ride and again it just seemed not to fire. I tried two relatively short starting attempts with no firing. On the third try the lights on the instrument cluster went out and smoked emanated from under the tank.

Essentially, wires for the entire ignition system were melted. The wiring harness was toast. The points were burnt, the wire from the points to the condenser was burnt, the red wire to the ignition switch was burnt and the wire to the coils (through the harness) was burnt. Essentially, everything in the ignition circuit was burnt. I did test the starter relay and it seems unaffected.

Despite a careful examination, I cannot tell what caused the high current in the ignition circuit. I suspect that wires within the harness rubbed and shorted together, at first intermittently, then completely. I'm in the process of replacing the main harness, including the engine harness, the points, condenser and other miscellaneous wires.

Obviously, I'm not contending that this is the same problem you are experiencing, but sounds a lot like the symptoms I experienced before the big disaster.

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Steve in Kentucky
91 BMW K1 (caretaking); 87 BMW R80 (RS); 61 BMW R60/2; 66 BMW R27; 74 R90/6; 59 NSU Maxi; 71 Norton Commando; 71 BSA 250 GP; 66 Triumph TR6R; 61 Norton Manx; 59/61 Triton; 14 Triumph Thruxton

Kidasters
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Used to have a similar problem with my R90/6

This sounds a lot like the problem I used to have with my R90/6. In trying to fix it, I installed a Dyna III, I replaced the switches on the starter, I went through all the boards and relays in the headlight bucket, plugs, plug wires, coils and multiple batteries. Problem persisted.

Last year, I replaced the starter. Problem solved.

I bet your starter has a flat spot, or it is dying. Pull and replace the starter. You can find newer, smaller, lighter, cheaper than OEM, better starters.

After starter replacement, my problem vanished completely.

Andy
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Coastal BC, Canada
Joined: 02/12/2011
Posts: 22
Hard start - an update

Hi

Well I managed to solve the problem. It was a combination of things that needed to be fixed so I hope that my experience may help the next person struggling with this issue.

I tried tuning the carbs and found one responsive and one not. I took both apart and saw the PO had rebuild one carb and not the other. A strange thing to do I know, but anyway.... I bought a carb rebuild kit and replaced all the O rings, gaskets, both float needles, I gave all the passageways a good clean and replaced one rather corroded main jet atomizer, set the float height. The PO had also set the chokes up so that they were at the half way point when the choke lever was set to off. This made the carbs permanently rich.

I looked at the starter and found all the wires were clean and tight and the starter was brand new. Having talked to a BMW friend who had also struggled with a hard start issue with his BMW with a Boyer unit and he said start again and buy a Dyna III. So I bought and installed a Dyna III unit and found that I still had the very slow, labored, starter sound with a strange, intermittent, clunking crunch. The positive terminal on the battery was also getting pretty hot after 15 seconds of cranking.

Suspecting the starter was probably an issue I pulled the cover and inspected it more closely. In doing the diagnostics I hit the starter and shattered the nose of the starter clean off.... Quite surprised at this turn of events, I had the original starter that the PO had replaced (that, to be honest, looked fine to me) so took both to pieces and build one up from best parts of each. I installed the rebuilt starter and hit the button..... the bike chuffed into life with the minimum of fuss, settled down to a nice idle and the positive terminal of the battery remained cool to the touch.

Investigation of the shattered starter revealed that the sprag clutch on the throw out has seized solid. I suspect what was happening is that the engine tried to fire but the starter was unable to properly release and was essential stopping the engine running. I am sure the poor state of the carbs was also a contributing factor.

Looking through the paperwork that came with the bike the PO had continually struggled with very hard starting issues since a major restoration and had already swapped the original Boyer unit for a replacement under warranty, because the Boyer unit was suspected to be the issue.... The local bike shop was also involved and also couldn't track the source of the problem down.

I guess the take away's from this saga are:

Don't assume a brand new starter is any good. A hot positive terminal is a warning sign that the starter is drawing too many amps... Voltage drop to about 9v on cranking is OK.

The Dyna III ignition is probably a better choice than the Boyer unit. Others may have had better luck than me but, anecdotally, it sounds like if you have a choice, go with the Dyna III.

Carbs in poor condition do not help the situation.

Thanks for everyone that chimed in with ideas and support. It was a pain to troubleshoot, but I wanted to let you guy's know what the resolution finally turned out to be.

Cheers

Andy

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Andy
Saltspring Island, BC, Canada
1972 R60/5, 1973 R75/5, 1960 R60/2, 1981 Moto Morini 500, 1946 Harley Davidson WL45

srankin
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An answer to a question

Andy, you asked if there is a way to measure amperage or draw from the starter. Yes, you can use a wraparound/clamp on amp meter to measure the draw. Just clamp it around the positive cable from the battery to the starter. St.

Andy
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Coastal BC, Canada
Joined: 02/12/2011
Posts: 22
Thanks for this advice. I

Thanks for this advice. I will try this on my bike just to see what the draw is like on a functional starter. Great to have a bike that finally runs....

Cheers

A

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Andy
Saltspring Island, BC, Canada
1972 R60/5, 1973 R75/5, 1960 R60/2, 1981 Moto Morini 500, 1946 Harley Davidson WL45

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