Pre mix oil options for a road going Challenger.

[pushrodsingle]

What Ho, I've just bought a challenger MX4 250. I am not at all technically minded and intend to put it on the road. Is the premix oil (not ratio) critical? The chap I bought it from said it was Castrol. If I empty the tank, do I need to strip the engine (as per 4 stroke) and wash everything before I change to another type?

[Brian Thompson]

Pre mix oils etc.

For more info on this topic have a look at this thread (it runs over several pages.) Just click on this link and it'll take you straight there; http://www.greeves-riders.org.uk/for...t=premix+ratio

It's always worth trying a 'search' first as there may well be threads posted already containing the info you are looking for. Just click on the 'search' tab on the toolbar at the top of the forum page and enter your keyword(s). Note that you can search both 'threads' and 'posts' using this option, which may give more results-try both.

Brian.

[John Wakefield]

Oil

What Ho, I've just bought a challenger MX4 250. I am not at all technically minded and intend to put it on the road. Is the premix oil (not ratio) critical? The chap I bought it from said it was Castrol. If I empty the tank, do I need to strip the engine (as per 4 stroke) and wash everything before I change to another type?

If you are changing from a castor based oil to mineral or semi synthetic you will need to drain the tank before changing oil type. Dont know that you actually need to strip the engine, maybe flush it through with neat petrol by filling crankcase via inlet manifold (remove carb first) & the drain off via crankcase drain screw. If you are only changing the make or brand for the same spec oil then no problem. I would ask the previous owner what grade/ type of Castrol he used & then keep to that grade. It is likely to be Castrol R a castor based racing oil. This has a destinctive smell.

[Brian Catt]

Hi there, I'm intrigued by the MX4 on the road bit.....Why, just for the hell of it, or are you doing an ISDT makeover? If the latter I may have pics to interest you.

[156trials]

If you are contemplating extended high rpm road use then you will need to use a good oil, to help with dissipating heat. Best oils to use are fully synthetic race types designed for pre-mix applications. Most "fully synthetic" oils are designed to be used in oil injection systems and are thinned with up to 20% kerosene, to lower the viscosity enough to allow use in oil injection bikes, so are not ideal for pre-mix comp bikes.

Castor oils work well, but tend to mean the inside of a motor gets pretty dirty after a while, rings will become gummed up and exhausts will need service more regularly. In terms of performance castor or castor/synthetic blends are not quite as good as fully synthetic race oils. No need to strip engine or flush through when you change to a different pre-mix oil, just drain tank and float bowl.

A very good oil to use for any 2T pre-mix motor is Castrol XR77, and this also allows accurate plug readings to be taken if you need to adjust jetting, and are running on modern fuel. For road use a mix ratio of 50:1 will be fine using this oil, however 2T oils of this spec are not needed for trials or road engines, but should provide the best possible lubrication if you intend to use an MX bike on the road,

[MikeTizard]

What Ho, I've just bought a challenger MX4 250. I am not at all technically minded and intend to put it on the road. Is the premix oil (not ratio) critical? The chap I bought it from said it was Castrol. If I empty the tank, do I need to strip the engine (as per 4 stroke) and wash everything before I change to another type?

I use my Anglian regularly on the road for extended periods. I've switched from oil to oil and never flushed anything out. I use fully sinthetic at 50:1 and am currently using PJ1 (because and can get it with discount) but have user Pulolene, Silcoline and any number of oils - 50:1 no worries. That said, I treat the engine with a lot of respect and do not thrash it for extented periods - I cruise at about 40 mph, just as the Challenger barrel pinging starts!!

[john downer]

Challenger Barrell Pinging

I have done a lot off miles on fully synthetic at 30 to 1 but have never been brave enough to try 50 to 1 . At certain revs my 32A with a challenger barrell makes a noise a bit like marballs dancing on a plastic tray. I have checked for small and big end play but all seems ok. With that in mind I would like to hear from Mike [or any one] About the pinging he put in his last post
Thanks in anticipation John

[Brian Catt]

It's fin resonance. My Rotax engined Can-Am has lots of rubber blocks between the fins to stop it. Buy a handful of rubber doorstops and carve them to suit.

[46T Sprocket]

I have done a lot off miles on fully synthetic at 30 to 1 but have never been brave enough to try 50 to 1 . At certain revs my 32A with a challenger barrell makes a noise a bit like marballs dancing on a plastic tray. I have checked for small and big end play but all seems ok. With that in mind I would like to hear from Mike [or any one] About the pinging he put in his last post
Thanks in anticipation John

Hi John,

Very late follow up to this old thread!

It might be fin resonance, my Pathfinder has lots of it due to the excessively big cooling fins. I have them damped similar to the method Brian suggest. However though, It might also be detonation. Detonation can damage an engine.

Two stroke engines without a proper squish band setup in the cylinder head (such as the challenger head has) and a piston crown that doesn't match the outer radius of the squish band. (Challenger & Villiers pistons are flat topped and not domed so don't squish the gasses well) They don't squeeze the charge away from the outer edge of the cylinder towards the spark area nearing TDC efficiently. Consequently due to the high temperature produced at the outer edge of the combustion area. This design is very prone to pre ignition of the fuel mix gasses. The pinging/marbles in a tin noise is the fuel igniting before the spark fires the compressed gasses. It can be damaging as it is forcing the piston back down on the up stroke before the proper ignition phase. A proper squish design runs much cooler at the edge of the cylinder and suffers much less from detonation.

An engine designed for low speed plodding with a bit of high rev work like in a trials Villier engine, don't show a detonation problem till the engine is used for longer periods at higher rpm's. For example, when the SSDT used to leave Edinburgh and the bikes had to be driven to the sections up north many of them never got there due to engine problems of this type. Curing the problem in that engine type is not very easy due to the design limitations of the combustion area in the cylinder head.

Villiers engines used for Scrambling and road racing had in later designs a more efficient squish design. In the 60s you could buy aftermarket cylinder heads of a better design to fit to your Villiers engine. Cylinders too. Greeves as we know made their own cylinders. This was still not perfect though as the pistons still had a flat crown. Later Villiers engines like the Starmaker and Greeves own in house designed Griffon engine** had domed piston crowns that matched up to the squish area in the cylinder head and consequently suffered much less from detonation.

David.

** Perhaps copied from the Villers Starmaker engines they tried and said where not suitable for use? Just a thought.