Ok. That is some great advice. Thank you so much for that.
so going LIPO it is.
With NIMH I kinda know where I am.
But know the theories behind lipo. I have a programmable charger which has all the plugs for LIPO. So what brand should I get? Something that's not going to kill my wallet. Mid range? And mind I'm in the UK

I have been using a Imax B6 variant that I got used and it suits my charging needs. I do not have antyhing above a 3s lipo.
Just about any lipo can last as long as you take care of it.

What about this?
https://hobbyking.com/en_us/turnigy-nano-tech-5800mah-2s2p-30-60c-hardcase-lipo-pack-roar-approved.html
Seams a good price. And ROAR approved

I do not know about the larger Turnigy batteries but the smaller 2s lipos have worked fairly well for me. If you want to race a Roar approved battery is ok but other than that for a basher battery it does not really matter. Really choose any battery brand you want. Just don't overdischarge it, leave it hooked up in the rc and leave it fully charged for long.

Just ordered 2. And a charge bag.
and reading up on safety and so on.
I will report back and let you know how it goes once they arrive and I get a run in.
Thank you so much for the advice. Just giving me the term "cogging" has helped so much researching the problem.

Yeah read up on safe use and charging of lipos and report back if your issues have been resolved.

Well. just reporting back.
LiPo's arrived and charged them up.
Still getting cogging ??!!! so i am going to invest in a sensored brushless motor instead.
On reading up if it is sensored it no longer Cogs.
Would this be correct?

Cogging is only at low speed. have tried different settings but still the same.
However once its moving it goes like a rocket!! so it is a million times better

Yup, being sensored will fix the cogging. Any sensorless RC car will cog at a low speed.

I'm necroing this thread because i'm just trying to bring a bugsta back to life and I might know what the problem is here.
The center drive dogbone can move forward and backwards, that makes noise that a couple of o-rings in the dogbone cups can fix.
but I discovered that the bearing bracket that slots into the motor mount in this bugsta was missing, meaning the spur has up and down play !! I thought I had the mesh right and all when I destroyed the 2nd pinion, but then i discovered the spur wasn't fastened down.

River Hobby 10200 Bearing Bracket (FTX6262)

If that's missing, you were so close looking at the spur bearing but not quite there. I'm not ready to give up yet since I just got it haha. Maybe its yours