At last!...

[Manky Monkey]

Been an uphill struggle ain't it Rod. Let's hope the finishing line's in sight now.

[minimutly]

Without wishing to upset anyone, I have to say you are wrong morrag. If you remove the original paper filter and either remove it altogether, or replace with a pancake, you will definately weaken the mixture - no two ways about it.
If you don't want to mess around with needles, replace the original filter.
I agree though, weak mixture is unlikely to be causing overheating, at least at the loads and power levels you are running.
Sorry to be controversial, but that's how I've allways seen it

[kapri]

Yeah , I do avoid stuff, but the trike is probably a long term contributor to the prob.could go on but this aint a agony aunt forum .I did summat really positive this pm though,so thats an achievement.

I know that feeling well Rod as I now also suffer ( past 3 years or so ) . You may be surprised by how common it is amongst creative types as well

[morrag]

The quote I read was "if you are running a pancake filter even with foam it will make your mixture weak" so I am afraid we are at cross purposes here, as there appeared to be no mention of using a foam filter, in place of a standard paper element, I assumed that the foam filter was fitted in place of no filter,with the Su being set up in the first instance accordingly, however, each to his own...." Morrag

[minimutly]

I was so disturbed to read how this is causing you so much grief Rod, I went back and re read everything I could about this. And from doing this, a couple of things jump out at me, aside from the various theories bandied about on cooling techniques etc. the reason for saying this is the reported lack of performance.
Two things you need to check, without driving out the gate

1 ignition timing/operation of advance weights. You need to mark up the max advance of your engine on the front pulley with some tipex/paint. I guess this is around 30 degrees? You can do this withe a sowing tape measure and some simple maths, or even by eye for now. The marking needs to show the "before top dead centre mark".  Once your happy with the mark, start the engine, disconnect the vacuum tube and hold the timing light on the marks. At an educated guess, by 5000 odd rpm your white mark should have moved along to the tdc pointer. If it hasn't moved, the weights have seized in the dizzy. If it has moved, but not enough,  and was still moving when you chickened out on the rpm, are you giving it enough revs? If your happy it's reaching max advance, but not as much as it should be getting, adjust dizzy position.
All this takes some reading, but is simple enough to do in practice. You can refit the vacuum advance and watch the timing move, or I normally suck on the tube to see it advance before refitting. A good suck might move the firing point 10 degrees or so, but it depends on the spec of the dizzy.

2. Once happy with timing, REFIT STD FILTER. This is really important, especially since the std reliant filter probably wasn't designed with performance in mind, and will be restrictive. Beg, borrow or buy one frome someone. If you want I can have a look if I have a mini one you can borrow, but idont know if it will fit below your tank?
Once the std filter is in place, start the engine, warm it up, and, after checking for any air leaks, adjust the idle mixture. Screw the jet in(up effectively) until the idle speed starts dropping, then back out for max idle speed.  If the engine note starts getting a rhythmic misfire, with associated eye watering fumes your way too rich. An uneven missfire is weak. Have a play and a listen, it's really quite obvious to see. Anyway, Leave ithemixture at fastest idle for now. put some 10/40 engine oil in the carb dash pot, give it a couple of blips to see what it sounds like. If all is well the engine should sound as crisp as reliant designed it. If not go back over these steps again. The fastest idle speed might be a bit rich, but it will be safe and not cause any overheating.
Take the trike for a spin. without getting into cooling discussions, the rad should get enough air without the fan running at anything over 30 mph, unless you have a 10 inch wide front wheel, or something blocking the airflow?
If the timing and mixture are correct, as above, and it still overheats, then you have other issues -ie stat not opening (feel the top, middle, bottom of the rad), restricted airflow (same check), blocked/too small rad.
Eliminate one thing at a time, you'll get there.
Huw

[ROD]

Ok, I see what youre saying thanks.I'm trying to get a reliant airbox, but had no luck.chopped the old one up and binned it! I cleaned and rebuilt the dizzy ages ago, and it all seemed to work ok.On my recent test run the engine idled and ran better than ever, it pulled really well in places on the route that it didnt previously on the same route.Understandably, due to gearing, it doesnt want top gear at slower speeds, but it doesnt bother me.

[ROD]

Sorry to pester you lot again.....Just to get this clear...It will be better to fit an original air filter box?? Im asking cos my carb is facing away  from rocker cover ie turned at 180 from original, therefore,I may have airbox clearance issues, which might mean cutting the airbox slightly to fit...I just dont want to waste more money and time.......OR......I could get a reliant air filter and make a box? What about aftermarket filters (not basic pancake) eg like Craigs?
Thanks for everyones time.

[terry t]

Rod I would leave the carb and filter as is. you don't want to create more issues by altering then. its been said earlier carbs are not causing it to over heat nearly all reliant engine trike are not running on original air box.
just get out and ride it to see if its ok 

[digger06]

looking good, two 5 mile runs and no overheating is a good point to be, leave the filters and get out on it more, I,m wi terry on this...
more road testing needed before anything else imo,
ride it like you will in real life, don't try to MAKE  it overheat,
good luck, your getting somewhere.................

[ROD]

Good point re trying to make  it overheat

[minimutly]

   
Re: At last!...
« Reply #127 on: Today at 09:21:23 AM »
Rod I would leave the carb and filter as is. you don't want to create more issues by altering then. its been said earlier carbs are not causing it to over heat nearly all reliant engine trike are not running on original air box.
just get out and ride it to see if its ok
But the point is, there is no filter! On an su carb which relies on the balance between manifold vacuum and upstream pressure, this will be crucial.
Even a K&n filter will upset it. So unless you have the capability to correct a weak mixture, leave the original filter on it. Once everything else is tested out ok, then start messing about with filters, but be prepared to replace needles - does no-one have a recommendation? As Terry says, not many trikes run std air box.

[ROD]

Ok guys thanks.Im listening !! 

[morrag]

Rod, I have run variable venturi carbs, as the SU is, with all types of filter, and none at all! and generally have only had to make the usual adjustments to the jet/needle relationship, to achieve acceptable mixture strength, indeed far more troblesome over the range of running with an SU, is too high a float level, or non seating float needle valve! but there you go, that doesnt solve your probs. however, I seriosly doubt that they are caused by fueling, and assuming, as I have said previously, that you are not running drastically retarded, I'm afraid your probs. are elsewhere, sorry ..Morrag

[scannerzer]

the nut on the underside of an hs su only controls mixture a idle through all other throttle positions the needle position in the jet is in control,a thicker needle will produce a weaker mixture an must be changed to suit. experiance mini tuners can profile a needle to suit any and all tunes of engine ,this may well not be Rods problem but it will have to be addressed at some stage

[morrag]

Er, I thought that's what I said, but like I also said, " yer pays yer money..." Rod, look elsewhere,as "Mr Reliant" selected a suitable needle for his motor, I'm sure! anyway, I shall retire......however, if you were but closer, I would fix it for you ..Morrag