Hitchcocks Forum

last Saturday, when it was reasonably warm, I was travelling 2 up up the M1 for a few miles.. we'd been a 15 run down it no problem earlier.

The bike, a 4 speed drum brake model 2006, was going well and I let her creep up to 70mph on the clock occasionally. Very suddently, she slowed then nipped up solid. I managed to catch it with the clutch, free wheeled on the hard shoulder for a few hundred yards and let the clutch out slowly.. she fired up and ran well again, so I coaxed her home.

I checked the oil and took her a 30 mile trip on Sunday, and still good. Changed oil n filter last night and no big lumps fell out!

is this a common thing? was I just lucky to not sustain any serious damage?

the old oil looked quite good but there was some emulsion in the dip stick channel.. where would this have come from?

Emulsion, aka "mayo" is very common on these machines, the oil just not get hot enough for the water to evaporate away and if ever it does the breather system which is designed to prevent the escape of any hydrocarbons from combustion, also prevents the free escape of the water vapour. On one oil change I had almost a pint of water under the oil when it had settled out. The only effective way to prevent this problem is the change the engine breather system so that the water vapour can escape and very frequent oil changes. Also I would suggest that 70 mph on the motorway is probably pushing your luck on these old machines, even given the optimism of the Indian speedo. Of course someone here will be along shortly to say their machine cruises all day at 80+ in the outside lane...

Quote : Of course someone here will be along shortly to say their machine cruises all day at 80+ in the outside lane. I don't know about that, but mine will reach that speed, if pressed. Regarding the nipping up, as long as the engine was caught in time - clutch in and throttle off before stopping and locking up, it should be ok. I 'run in' some of my own engines by taking them up a steep hill under full load [not slogging as in another post by me recently] until I feel them starting to tighten, then back off on the throttle, change down and run under very light load, to cool off, before repeating the process. Stripping the top end and attending to 'tight spots' on the piston skirts and bores, makes for a fast engine very quickly without having to rack up loads of miles. If your bike is still running ok, then it is ok, don't worry about it. Regards, Paul.

many thanks Guys.. the oild and filter, whilst dirty, showed no obvious signs of lumps of metal, nor did the 2 brass strainers attached to the sump bolts

Any piston that 'nipped' (seized) will have suffered extreme heat damage that has 'killed' the temper of the alloy, as well as physical deformation. The rings will be scrap, and bore will look like it has railway tracks up and down. At some point they will have to be cleaned up (honed), mean time you will experience excessive 'blow-by' and increased oil degradation. (How old was the oil when the piston grabbed?)


It the bike is a 500 running the factory piston, replace it as soon as is possible! It wont last much longer...


Yes, you can continue to run the bike as it is, but DONT ride it hard! Not least due to reduced ring efficiency and Blow-by blowing/burning the oil off the bore, and the piston will be inclined to seize further when 'pushed'.

Interesting, we have two Bullet experts with different opinions, who is right?.

Well I am not a Bullet expert but have been tuning british bikes for many years now and although the Indian Bullets are not on my tuning list, I have been reading what people on here do to them and from reading others posts it would seem that the Indian Bullets come in to the UK set up to run very lean to pass emmision regulations, this is a prime cause of overheating and if I were to buy one the first thing to address would be setting up the carb correctly, 1/ bigger main jet, 2/ reset needle height.

Did the piston seize and then free off in a few hundred yards of coasting?, I doubt it, when coasting the outside of the engine cools first due to the airflow over the fins, this would shrink the cylinder slightly causing it to tighten onto the piston even more not releasing it. the best thing to do if you think the piston is getting tight is close the throttle and put the choke on, the extra petrol cools the piston first and it shrinks again.

I am with BW on this if the bike is running OK and not showing any lack of compression or excessive oil use, keep riding it, show it some extra care for a few miles and see how it is.

Is 70mph too fast?, we it shouldnt be, correctly set up even the 350 should have no problem.

Revband without a lot of beefing up of the guts of the engine, you would be lucky if a 350 Enfield would do 70mph, let alone maintain it without self destructing.

Here is an Enfield which nipped up on the dyno and once again, shortly afterwards on track, during a race at Anglesey, after this it actually WON two races at that event. Back at home, the top end was stripped, the bore cleaned out and honed by hand, with emery cloth. The piston skirt area which had picked up was attended to with a fine, flat file. Here it is, having been reassembled with that same barrel and piston. The day this film was taken, it was pushed, twice to 9000 RPM and can be heard going past 8000 RPM in this video - there is no smoke, rattles or leaks, it is ready to race. Form your own conclusions, folks.
https://www.youtube.com/watch?v=MlIZL0RCvxs

I think there is a bit of difference between a slight nipping and a total seize. I've achieved the second too many times mostly on the old 51 350 and have generally replaced the piston. I did relieve the high spots and return it once but the fact that it had a totally blocked oil way to the big end meant that it soon seized again. Made the fatal mistake of assuming that it still had the original floating bush big end which would have very quickly indicated such a blockage however in truth it had a roller big end and whilst getting a might hot wasn't giving up.

I nipped up my 350 when it was running in from new. It seemed to run OK afterwards so I left it alone. I did a top end overhaul at 10,000 for a cylinder head gasket leak and barrel/piston/rings were fine - just reused them.
70 mph on a 350 is really at the top end of it's capabilities. I've had mine up there, but not for long! Of course, it's less likely to blow up than the 500 when pushed.