Hornby Class 37 stuttering

[Smudge617]

Hi All

I am my wits end with this model and I'll explain why.
Let me first say that I have cleaned the wheels/Pickup's, and track several times now, and completed a service.
and its fitted with a Hornby decoder R8249
So, the problem, when powering up, the loco wont move for about 5-10 seconds and I have to "push start" it, then it will stutter round my layout for around a minute and then is fine most of the time, until I stop, reverse is worse, basically not a good idea, does the same but for far longer period and often doesn't move but hums, then suddenly takes off like a rocket.
I've checked all my connections with a multi meter (I use a harness) again, several times, fitted three different decoders (Hornby R8249 (not the one currently fitted) a Laisdcc Kung Fu series and Zimo MX600R), and encounter the same problem, but weirdly, when not on the track, and power is applied direct to the wheels it runs like it should with all three.
I've run all my other loco's on my layout and all run without a problem just this one.
Is this a case of lost cause, find a new motor, or does someone perhaps know a cure.

Your thoughts would be appreciated on this.
Thanks

[Mick Bonwick]

If it was mine I'd check the back-to-back measurement of the wheels on each axle. Instead of push starting it try just twisting the power bogie slightly on the track, thus forcing diagonally opposite wheels to contact the track.