Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: El__burro on July 07, 2016, 01:00:13 PM
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Good day, I am struggling to start the bike with the push button.
The bike (k2) starts easily with the pedal and all lights, indicators and horn are ok.
I have had a look at all the wires to see if any shorts on the frame but nothing seems wrong.
I guess it doesn't recharge the battery either.
HINTS
Starter relay clicks so I assume it works fine.
When I press the start button i hear the buzzing noise but no cranking.
Battery is full (14.5v) but as soon as I remove the charging cables it slowly drops to 12.2v then around 9v once i turn the key.
Not sure if it matters but a few weeks ago I had to rewire the ignition switch, could this be the cause?
Help please,
Thanks
el__burro
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Try cleaning and tightening the battery leads at the battery end and the solenoid ends, and be certain that the frame is rust and paint free where the earth lead attaches.
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If the vo;ltage drops that low, try jump leads from a car battery, you could have a duff cell on the battery. If it works, you need a new battery
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Thanks,
tried both, but still no success.
El__burro
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Have you tried shorting the terminals of the solenoid together and see if it turns over? If that doesn't do it, time to take the starter motor off and bench test it with a known good battery, luckily an easy job to do.
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I have bridged the two solenoid terminals and it does a little spark and I can see some fumes coming from the (sealed) battery; still doesn't turn the motor.
Could it be shorted somehow?
thanks
el__burro
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Possibly. I would remove the starter (remove cable from solenoid, remove chrome starter cover, then 2 bolts from starter and lever starter to points side of bike about 20mm, then lift out) and test with a known good battery. If it doesn't work then, time to see what state the brushes are in (not too expensive ;D) and replace if badly worn, or buy a s/h starter motor. Good luck.
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I can see some fumes coming from the (sealed) battery;
i would say your battery is toast and get a new one any voltage reading under 12.6 and the battery has had its day in my book
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I figured using a car battery would preclude this possibility, but a new battery sounds a good idea, but the motor needs checking if it didn't turn on a car battery
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tried the car battery but it has made no difference,
while the engine was running I pressed the push start button and realised that it was cutting off the engine.
Definitely a short somewhere, looked at push button and the hearth but it all good.
Ive tried to remove the motor but after removing both bolts it wont came out. (not really trying as I am sure it works fine [it did until this issue]).
El__burro
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You need to lever the starter toward the points side using a large screwdriver or similar, you will feel it pop out, then lift by the cable to get it out of the engine.
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I guess I need to remove the chain tensioner as i cannot remove the bolt undet it (and push the motor out of gear)
Can this be done somehow without removing the motor?
el__burro
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Try disconnecting the starter cable from the solenoid, connect it to a car battery +ve and then toch the -ve to the earth point on the frame or starter motor body, if the motor doesn't spin, it has to come out I'm afraid.
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Removed and tested, it feels like its DEAD. (soon i'll upload a video)
Is there any point in removing the cover to expose the brushes and check?
I guess ill have to source a sh motor.
Thanks
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Yes, remove the cover and look at the brushes, fairly cheap and easy to fix, not a lot else goes wrong with them.
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Managed to remove the cover, one of the brushes is much shorter than the other. (see img)
Could this be the problem?
Thanks
el__burro
(http://uploads.tapatalk-cdn.com/20160708/957c2fc04c6a92b65ba35e9055319b8d.jpg)(http://uploads.tapatalk-cdn.com/20160708/a79f5fa156fff42f64ad9261934730f0.jpg)
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by looking at the picture Ive realised that actually the brushes seem ok.
I took it apart and gave it a good clean, eventually it worked fine (tested on bike battery)
Once I put it back I have the same issue. I guess the battery (almost new) is to be replaced.
What should it read once i finished charging?
Thanks
el__burro
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When you say "it worked", do you mean the starter motor spun when connected up or did it turn the engine over?
In other words, was the starter motor back in the engine when you tested it?
Have you checked the starter solenoid by shorting out the big terminals with a spanner? What was the result of that test?
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by looking at the picture Ive realised that actually the brushes seem ok.
I took it apart and gave it a good clean, eventually it worked fine (tested on bike battery)
Once I put it back I have the same issue. I guess the battery (almost new) is to be replaced.
What should it read once i finished charging?
Thanks
el__burro
at least 12.6v after standing for a while,see this link
http://www.autobatteries.com/en-us/battery-care/testing/
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I cleaned the motor, i attached it to the bike battery and it worked for a second, then very quickly it slowed down until it stopped.
Tried again but the motor was not responding.
I tried connecting it to the car battery but it wouldn't work with the cables so i decided to touch the motor case on the negative battery itself and the cable from the motor on the positive of the battery directly.
It worked fine.
Unfortunately when i do the same with the bike battery it drains it very quickly.
Battery sits at 12.7v
el__burrohttps://vimeo.com/173963790 (https://vimeo.com/173963790)
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Your battery's knackered then.
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I've read that MF batteries are usually good (with regular use)
I have ridden my bike for less than 5 miles since replacing buying this battery.
I guess I need to test the charging system too.
Any advice on purchase?
el__burro
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I've read that MF batteries are usually good (with regular use)
I have ridden my bike for less than 5 miles since replacing buying this battery.
I guess I need to test the charging system too.
Any advice on purchase?
el__burro
do you have a charger/ optmiser ? and do you have it plugged in when your not using it ?
the worst thing you can do with batteries,is not use them,regular use,or maintenance charging helps alot
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Yes, i do have a charger, the battery is left connected at all the times.
(Not regular use of the bike means that I start the engine at least twice a week).
when I push start I see smoke coming from one of the briefing holes on top of the battery.
Battery reads 12.70v.
el__burro
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Yes, i do have a charger, the battery is left connected at all the times.
(Not regular use of the bike means that I start the engine at least twice a week).
when I push start I see smoke coming from one of the holes on top.
Battery reads 12.70v.
el__burro
smoke from electrics is always bad news,are you saying your getting smoke from the switchgear,starter button area?
you should be to check the wiring,and also by shorting out the solenoid see how the starter spins the engine,
more head scratching time !!!
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Buy a Motobatt Battery, Dave Silver will order the correct one for you ,cost around £40, my charge shows 14.5v ... the Motobatt also gives more cranking power.
Tip when fitting it make sure the ajustable terminals are really tight !
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I beg to differ on that score. Motbatt WERE good, but a few tears ago they changed something in the manufacturing process, and many die even before a year is up. Trigger can expand more on this problem.
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My Motobatt batteries have been very hit and miss the one in the Triumph Trophy is mounted on its side and can be left for months at a time and still starts without issues.But the one in the 750 turns over very slow after a few weeks but still usually starts.The one in the Guzzi is normally to drained after 2 weeks.But that may have something to do with the electronic gubbins.
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I have a Motobatt in my 400f that I bought in 2013. Never do anything to it and it's fine. Cranks very strongly on the starter and is good even after a long lay up.
The other day the battery in my VFR failed at three years old. Some brand called LP fitted by the po new. Never cranked that well. Just put a Motobatt in it so we'll see how it goes but cranking much better than the LP ever did.
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The smoke (fumes) come out of the battery when I push the start button or I jump the solenoid. (its a MF sealed battery).
Can anyone give me their opinion on MF batteries?
I guess I need to part with some cash but don't want to do the same every year.
Thanks
el__burro
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I have had MF batteries in the past they seemed to last long enough when the bike was in regular use.
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I have a Odyssey on my bmw r80 (no daily use).
it's a great battery but I can't find it for cb750 k2.
el__burro
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I have a Motobatt in my 400f that I bought in 2013. Never do anything to it and it's fine. Cranks very strongly on the starter and is good even after a long lay up.
The other day the battery in my VFR failed at three years old. Some brand called LP fitted by the po new. Never cranked that well. Just put a Motobatt in it so we'll see how it goes but cranking much better than the LP ever did.
Yes I agree, anyone can sometimes be unlucky & get a bad one, but there is a warranty with all theses things.
I have got 2 motobatt batteries on my bikes & they are the best most reliable battery I have ever had in 48 years of motoring, the cranking power is awesome.
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Buy a Motobatt Battery, Dave Silver will order the correct one for you ,cost around £40.
Cant find any MOTOBATT on DSS.
Any link?
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try Wemoto,
prices OK,not cheap,but good quick service
http://www.wemoto.com/bikes/
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I've been using Varta AGM units on a variety of cars and bikes, the oldest one did 11yrs and 120,000 miles or the family VW diesel, so way past any reasonable warranty.
They seem to have quite a good cca rating compared to general stuff around and also hold voltage well however low the usage rate of the vehicle.
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Buy a Motobatt Battery, Dave Silver will order the correct one for you ,cost around £40.
Cant find any MOTOBATT on DSS.
Any link?
No you wont find one on their website, as I said previously they will order the correct one for you but you will have to phone them, important to get the right one & right size to fit in the box, that's if its going in the stock space.
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Cant find any MOTOBATT on DSS.
Any link?
I got mine from mad4bikes via ebay, eg: http://www.ebay.co.uk/itm/400724825719
Check the correct model for your bike.
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thanks a lot, does it fit the k2 battery tray?
el__burro
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My K1 has a Motobatt MBTX14AU
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Buy a Motobatt Battery, Dave Silver will order the correct one for you ,cost around £40, my charge shows 14.5v ... the Motobatt also gives more cranking power.
Tip when fitting it make sure the ajustable terminals are really tight !
just called DSS (David Silver Spares) the sales person has ensured me that he hasn't never heard of this "motobatt" brand.
i have no idea if Dave Silver is the same person as David Silver.
How do I order the right one for CB750 k2?
Thanks
el__burro
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if DSS can't find a Motobatt
call Wemoto,they give great service
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Is this the right one?
http://www.ebay.co.uk/itm/280984121956?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
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Yes, Phil, that's exactly the one I bought. About £6 cheaper than VeMoto. A trusted seller too.
(https://uploads.tapatalk-cdn.com/20170421/76796ee1487b6ca5533dfea5f76b28f4.jpg)
Thanks
el__burro