SU carb paper air filter

I like the mod.....a really smart idea.

My Commando has a SU carb that originally came wearing a very fine foamy cylinder filter. This was washed each year and then oiled. It also had the oil tank breather passing through it and worked quite well until Ethanol came along and disolved it.

I then purchased a large KN type, cone shaped metal mesh filter. The cleaning instructions were the same with a yearly Paraffin wash and then an oiling. I was told that the oil helps to create an electro-static charge which makes the dust stick to the mesh. As before my oil tank breather is attached to the filter.

This set-up appears to work as when I pulled the pistons out, this year, to renew the rings the pistons and bores showed none of the fine scoring found in my unfiltered Dommie engine.

Hi

i used a standard back plate with single carb front plate with rgm narrower filter an inch smaller and made a plate brazed on a carb ring for and standard air box rubber to fit see picture.

Mick

another picture Mick.

Previously peter_shand wrote:

Hi Mick

Thanks for the reply. Just the information I wanted, i.e. that it had been done.

Is that a priming pump fitted to the float chamber? If so, where did you get it?

regards

Peter

Hi Peter

yes thats a primer its a briggs and straton lawn mower primer bulb with a base and cover i made up it works well its the type with the hole in and still acts as breather over flow got it off ebay.

Mick.

Previously Chris Grimmett wrote:

Mick,

The priming difficulties with the SU were one of the reasons I gave up with it and went to Mikuni. You seem to have solved this nagging problem.

Would you do a wrote-up for Roadholder together with some pictures so that everyone can know about it?

I have recently bought an SU kit for my 750 commando not fitted yet,how bad are the priming issues ? i had thought about using an aftermarket jet ski priming kit that plumbs straight into the manifold about £20 from evilbay ,i would love to know how you fitted your primer a write up in roadholder would be great cheers nick

Iâll add another vote for a write up with a few more details of the primer pump you used. I had the same problem when I first fitted my SU some 30,000 miles ago, but have found that provided the bore of the fuel tap was similar to that of the inlet stub on the carb, I have no difficulty starting. My routine is, from cold, fuel tap on, full choke, ease over compression a couple of times & then a good kick. This almost always results in a first kick start. When the engine is hot, the same routine but with no choke, & with a warm engine, same again but with just a sniff of choke. If I donât ease over compression a couple of times, then itâll take two or three kicks to start. I have since fitted an SU to a second Commando & find that the same routine works for that also. The problem Iâve found is that quiet a lot of fuel taps only have a very small bore through them, & this restriction seems to cause very difficult starting with the SU. Strange, as you would think that once the float bowl was full, that would suffice, but opening up the taps really did make a huge difference, effectively from not being able to start it at all, to pretty much first kick all the time.

As for air filters, Iâve run the K&N for probably 20â000 miles, like Phil, I wash it out & re-oil once a year or so & have had no problems & noticed no excessive wear to either carb or bores. My foam filter disintegrated years ago!

Regards, Tim

Previously Chris Grimmett wrote:

Mick,

The priming difficulties with the SU were one of the reasons I gave up with it and went to Mikuni. You seem to have solved this nagging problem.

Would you do a wrote-up for Roadholder together with some pictures so that everyone can know about it?

Hi Chris

will get some info together about SU carb mods i made primer,filter and throttle lever position etc Ken Weeks gave me the primer idear on last thread about SU and Tim Gostling helped out with info on taps and float level. PS a mk 2 primer is under way hopfully with no turning and not sticking out so far.

Mick.