X/F Splutter !

[genneton4]

Can anybody help ?
I have just bought a 1990 X/F factory Supersprint (135 bhp).  I really like the car but am struggling to fine tune it.
It splutters from initial pickup until it clears it's throat @2000 rpm - then it runs a dream.
I guess it has 'hottish' cam but I don't really want to drive it like I stole it all the time !!
Have tried lots settings with the idle mixture screws ... to no avail.
It has Luminition electronic ignition and I have put in a new set of plugs.
Thanks
Keith  
 

[Alan.gilford]

Hiya, I have a 92 crossflow and if you are not an expert on twin 40's best to start here 

http://www.s262612653.websitehome.co.uk/DVAndrews/webers.htm

Better still if you can find a rolling road near you that still does carbs you will get the best results there.

Should pick up from idle quite smoothly once set up and balanced correctly.

Have you checked jets, emulsion tubes and choke size ? 

[Golf Juliet Tango]

Unless you know exactly what you are doing, I would get it set-up by someone who does.

By all means learn as much as you can at that time and try things out, knowing a good point to which you can return.

[Stridey]

A few things to check if you can.

The Weber’s have gaskets to the manifold, which should have a small amount of ‘play’, how much, hard to say, but enough to jiggle firmly by hand, you can replace these gaskets with ‘misabs’ which have built in O rings. If air can get in between manifold and Weber’s you may get splutter, they can rot over time. These can be replaced yourself, just awkward to get to bolts if big handed.

Buy your self a balancer and watch some vids on balancing carbs. It’s not too hard and useful to be able to do. 

I like to run 96/98 octane fuel.

Things like internals, floats etc I leave to my local 7 servicers, Ratrace and Chris Wheeler in Herts I can reccomend but any good old school racy type garage should be able to check the Weber’s.

 

[Stridey]

One other thing.

To start I turn on car, listen for pump, press throttle 5 times, then start.

it will splutter a bit, but by the end of the road it’s running fine.

[leo_71]

A while ago I had a very similar issue to yours. I didn't check the ignition or attempt any adjustment to the carbs at the time, but instead made a mental note to investigate the problem before the next outing. A week later, with the bonnet removed, I started the engine and noticed the middle exhaust gasket blowing so removed manifold and found that the middle of the centre gasket was completely missing. A bit of fettling later and new gaskets fitted the engine ran really very smoothly. Out on the road the difference was remarkable, no lumpiness just smooth response through the gears. Just a thought.

[genneton4]

I think you may have something here - I will investigate !

Keith

[genneton4]

OK - manifold not blowing - although it does look crusty !   I can't see or feel anything.

Forgot to add - went for a run this morning - the car does 'backfire/cough' through the exhaust at regular intervals - not under stress.  Also, same through the carbs !!

Surely this must ring a bell with somebody ?

Keith

 

 

[orangepeel61]

I suggest you sort out as much as you can yourself before investing in a rolling road, there's plenty of information on here if you do some research. 

If your ignition system and timing is ok then popping and banging exhaust and spitting carbs are both indications of a weak mixture.

The splutter you talk of could be a number of things, carb balance is an obvious one and worth checking anyway.

Pump jets maybe to large, if your supersprint is original it is probably fitted with 45s, more appropriate would be 35s. The larger jets cause too much fuel to be pumped in resulting in bogging down on take off.

Also look at the idle jets, again if your car is original it's probably got 50f8, in mine I put 50f9 (larger) and it made a huge difference. 

Good luck

Neil.

 

[genneton4]

Thanks Neil.

I think the engine is all original.  It is a 1990 Prisoner car.

The Carbs are 40's.  The idle jets you speak of are F845 !?

Just as an aside - the car was tuned by Kenrick cars in Wales and I found the plug gaps to be 30 thou - I replaced with same gap.  Is this too much ?  Visiting various threads it seems that a smaller gap may help ?

 

Keith

 

 

[Gloucestershire AR]

Best advice is probably to seek out a local 'old fashioned' garage (not sure which part of the UK you are). Kenricks are very good (and lots of Caterham experience) and if you're local to them, may be worth having a chat to them. But any older mechanic used to old Ford Escorts and the like will be ideal as they will use their experience to find out or know what's wrong rather than any technology (of which there ain't a lot on a Crossflow!).

Crossflows do often pop and bang on the overrun anyway - depends how they are set up and worse if there are any exhaust leaks. Which plugs did you fit? I use NGK BP7ES and they cover most road situations. Anything with an 8 may be more competition biased and anything with a 6 may not be suitable. 

I suspect this is nothing major and wonder whether a carb balance (as suggested You Tube is helpful) may be a good starting point?

Good luck - great car and great engine too.

Andy (fellow Crossflow-er)

[orangepeel61]

Hi Keith

When I got mine 4 years ago it was running like a pig, over time I have fettled it to the point it is running really well. I do still have a slight hesitation at take off, wouldn't go as far as to call it a splutter but still working on it. Hadn't seen the threads about plug gaps, mine are at 30 thou, something for me to look at.

Your idle jets sound too small to me, you should get a steady and strong increase in power as you go up the rev range. The main jets should kick in at around 2500rpm or so, if you get a surge of power as the mains take over it suggests that the idle jets are not delivering enough fuel, the transition should be smooth. This is one of the problems I had, I found some 50f9 jets new on eBay for about a tenner and just tried it, the difference was phenomenal. 

As I mentioned previously check your pump jets, they could affect your splutter.

Having said all that, with your exhaust popping and carbs spitting your basic fuel setting is too weak, if you richen the carbs by say an eighth turn you'll notice a difference. Do it carefully so if it makes things worse you can put it back!

Neil.

 

[HendrixsWhiteStratReturns]

to the OP

 

Hi mate - I have a 1990 1700 XF Supersprint and had a nightmare with the same issues you describe plus a misfire that had me tearing my hair out

James Whiting sorted the car for me but the problem seemed to come from several areas and the key issues seemed to be:

- Carbs needed refurbing (twin weber 40s)

- Plugs keep fouling ( now run NGK BPR6EIX and they are superb)

- Ignitor unit in the Aldon Dizzy was kaput

 

Hope that helps

[genneton4]

Thought I'd sorted it.  25thou Spark plug gap.  Got all the plugs the same nice colour. Just been for a blat and it's still there.  Any adjustment of the idle mixture screw (which is all I have to play with) doesn't appear to make that much difference. 

I'm currently on 4,5,5,5 half turns out from stop.  Is this about right ?

Some say intermittent spitting through carb and exhaust point to the car running too weak. (Spits about every 30 secs on run randomly).

Should I try maybe 6 or 7 half turns out from stop ?   What is the norm/average ?

There aren't garages within miles of me (Nottingham) to tune the carbs for me.

If I had hair - I would tear it out.

Keith

 

 

[Tazio]

Stop faffing, take it down to Troy at Northampton Motorsport...he can sort it, and you can watch and learn.

[genneton4]

Thanks Tazio, the feeling of achievement when you've sorted something out for yourself is immense, instead of chucking money at it.  You ought to try it sometime.

Been for a second blat and Neil was right - mixture too weak (plugs beige).  Tweaked to 6,7,6.5,7 half turns - back to 30 thou plugs.

Not perfect but immeasurably better.  I don't think there is a perfect running 135 bhp Caterham.

Keith

 

 

[Tazio]

If you dont know what you are doing, then paying, and watching someone do it properly so you can learn is always money well spent. Continually faffing and hoping to stumble on the solution is just that, faffing.

[Roger King]

If you are running 45 F8 idle jets they are far too weak and will cause horrible flat spots before the main jets kick in. Standard Supersprints run best on 50 F9 jets which have a larger fuel hole and a smaller air hole. Make sure also that you have 35 pump jets. It's very common to find they have been swapped for larger ones which do nothing except waste fuel and make the engine stumble when you open the throttle.

All the above assumes a standard Supersprint spec engine with otherwise unmolested carb settings. You do of course need to ensure that carbs are balanced and otherwise set up properly.

A well set up Supersprint is perfectly capable of being driven around a multi-storey car park with no bother at all. Getting an engine to run well on full throttle is the easy bit - it's the low rev, light throttle stuff that requires a skilled operator.

[Tom_Arundel]

Check that the carb mountings are not too tight against manifold. It causes fuel frothing and lean mixture if they are.

[HendrixsWhiteStratReturns]

 

Keith - check out Roger's post above on jetting.That guy really knows his stuff on Xflows 

[genneton4]

Hi, guys, thanks for input - especially Roger - this sounds like it !!

Will try and find/order some 50f9 jets now.  The pump jets are 35.

Keith

[orangepeel61]

Keith, Here's where I got mine:

https://www.ebay.co.uk/itm/NEW-4-X-size-50f9-Idle-Jet-Weber-DCOE/172990586269?hash=item28470add9d:g:NSMAAOSwll1Wxcot

When fitting the idle jets don't push them all the way into their holder, put them in far enough to locate and then let them find their own height by screwing them in place (hope that makes sense)

I've picked up so many useful tips from Roger, he knows what he's talking about.

Neil.

[genneton4]

Thanks Neil - I ordered the same ones this morning.  Thanks again for your help - I think you twigged my problem first.

Keith

 

[genneton4]

What splutter !!

New 50f9 jets arrived this lunch, fitted, car runs perfectly.  Don't know how the 45f8's got in there.

Thanks to all who contributed especially Roger and Neil.

Well faffed I think.

Keith

[orangepeel61]

Great news, well faffed indeed! I can't take any credit, I was only relaying what I'd previously learnt from Roger!

Enjoy!

Neil.