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Starter engine not able to turn - Yamaha 5PW
krestudon - 11/4/18 at 03:14 PM

Hello all,

I've broken the 2nd gear on my Yamaha 5PW powered MK Indy, so i decided it'll be easier to swap the whole engine.

Bought a whole '03 5PW, that i was told to work but cant be verified.

Swapped the engine, just to find the starter motor, not being able to turn it.

I've tried both starters (from my old working engine) and both do the same.

If i remove the spark plugs, then starters were able to turn happily but as soon as i screw them in again, both starters show like being not strong enough.

I also tried bypassing all the wiring, by jumping with some battery cables, the starter motors directly to the (fully charged) battery.

Do anybody has any advise i can be given on what's happening or what to try next?

Thank you in advance!

fazerruss - 11/4/18 at 05:14 PM

I'd be inclined to take the cam cover off and check valves and timing is correct.

CosKev3 - 11/4/18 at 07:45 PM

Does it spin over really fast without the plugs in?

02GF74 - 11/4/18 at 09:38 PM

quote:
Originally posted by krestudon
, both starters show like being not strong enough.



That is a misleading conclusion, I am sure yamaha designed the starter to be capable of the task.

The problem has to elsewhere.

Is the battery charged, in good condition and of sufficient capacity

Are the cables refitted correctly with good glean connections.

If it was working before, check again the cabling.
.
Does engine turn when you connect directly to the starter.

How does it feel when you turn engine over by hand

krestudon - 12/4/18 at 08:30 AM

The engine was supposed to be good, so didnt thought about checking valve timing, but maybe i'll have to do it at the end.

Yes, engine run fast and freely without plugs.

quote:
Originally posted by 02GF74
quote:
Originally posted by krestudon
, both starters show like being not strong enough.



That is a misleading conclusion, I am sure yamaha designed the starter to be capable of the task.

The problem has to elsewhere.

Is the battery charged, in good condition and of sufficient capacity

Are the cables refitted correctly with good glean connections.

If it was working before, check again the cabling.
.
Does engine turn when you connect directly to the starter.

How does it feel when you turn engine over by hand


Yes, i wasnt suspecting on the starters, as i have two, and the one on the previous engine, worked perfectly before change.

As i have redone part of the wiring i'm pretty confident on clean new connections, but to avoid any possible starter relay failing, or something else, i am now trying by directly connecting starter to battery possitive, it sounds as trying to turn, but not having enough force.

Don't tried to turn engine by hand, as i dont find an easy place to make it turn, but i'll try today...

adithorp - 12/4/18 at 10:21 AM

Could be s poor earth. Have you tried with jump lead to both positive and neg (direct on engine)?

motorcycle_mayhem - 12/4/18 at 12:43 PM

I've a similar view - check the earth?

If it's earthing through the throttle/clutch/gearchange cables and not through an intended 16mm electrical cable, you'll be struggling to supply the motor with enough current under load.

These engines spin freely on 12V with aftermarket high compression pistons and aggressive timing, so something's amiss.... externally or internally(?).

Bigboystoys - 12/4/18 at 02:28 PM

If it's stiff to turn with the plugs out and the block has sat for a while it might be the bores/internals are dry of oil. I would certainly be cranking it with the plugs out until the oil pump has circulated it a bit might even need a quick squirt of a light oil in the bores to free it up

nick205 - 13/4/18 at 11:02 AM

Seems odd that it spins with the plugs out, but not with them in.

Do you have a compression tester?

If you do a compression test may show you more maybe the camshaft is worn and not opening the valves properly so the compression is too high.

https://www.ebay.co.uk/itm/Petrol-Engine-Cylinder-Pressure-Tester-Car-Motorbike-Compression-Gauge-Test-Tool/1230689 14261?epid=9017812911&hash=item1ca77a9a55:g:XZMAAOSwfZFazDHm

[Edited on 13/4/18 by nick205]

krestudon - 13/4/18 at 02:04 PM

Some good points, thank you guys.

I'll try removing the plugs again, and turning it some more. Also doubling the engine earth, and if i find my old compression tester, i'll check compressions. Hopefuly we can get some conclusions.

krestudon - 15/4/18 at 07:04 AM

Find some weird things...

First i removed the spark plugs and find that the starter was not able to turn the engine.

I suspected the battery, although charged the last day, was failing, so i borrowed the battery from the car.
Cabled it to the starter and at first touch, it started to melt the battery terminal, so stopped.

Then i selected first gear and started pushing the car, so making the engine turn.
Its the first time i've pushed a car without spark plugs, but seemed hard to me.

Connected the car battery to the mk indy wiring, instead of directly to the starter and tried again.
Engine turned happily. Refitted the spark plugs, and the same, the engine turned happily.

Did some videos, but i dont think they're of any interest.

I have buyed a new bike battery and will change it tomorrow.
Now i have to finish fuel pump wiring, and then try to start it.

Thank you guys!

MikeRJ - 15/4/18 at 05:55 PM

quote:
Originally posted by krestudon
Then i selected first gear and started pushing the car, so making the engine turn.
Its the first time i've pushed a car without spark plugs, but seemed hard to me.


It will be hard to push in first gear, because you are trying to spin the engine many times faster than the wheels. If you had used e.g. 4th or 5th it would have been easy.