16v on Bike carbs - emissions trouble!

Hi,

Trying to get my mk1 thorugh its MOT - but I can't get it past the emissions test.

It's a 1.8 (bored to 1.9) running on GSXR750 bike carbs. The CO level is ok at the moment around 2.5-3% but the HC levels are around 2000!

The mixture was leaned off to get the CO down but it raised the HC (it was at 5% CO and 1200HC - not good either)

It has a Bogg Bros manifold on it and they serviced the carbs at the same time, and said they were in good nick and setp fine for my engine. I never got round to taking it back for a proper tune-up though.

The fuel pump is a Facet Red top running 3psi.

I believe the overbore and pistons were done in the last 18 months and it doesn't smoke at all.

What areas should be my first port of call to check? On tick-over it sounds a little lumpy and pops and farts fairly regularly - does this suggest overfueling?

I am going to change the plugs and oil as they are well overdue - should this make a massive difference or is likely to be the carbs or something else?

Any thoughts or suggestions gratefully received.

Cheers

 

im in the same boat with my mk1 9a on 45 webers! what cams are you using just out of curiosity? i was using a kr exhaust cam in the inlet and decided since it wasnt timed correctly it would be letting a lot of fuel through. Ive swapped the cam for a kr inlet one but i think its still letting too much fuel through to pass. I think the only thing to do is to get it on a rolling road and set up properly with a CO2 sensor up the exhaust.

 

Apparently the head was rebuilt at the same time the engine was done - standard cams AFAIK.

I guess ultimately I will get it rolling roaded - I just want to get it through it's MOT first so I can drive it around legally to get other bits and pieces done before I shell out on and RR session.

Cheers

 

yeah my thoughts too! wondering how to get it to a rolling road with no tax or mot!

 

try taking it to a more 'friendly' mot tester? at least you could get them set up properly?

 

have you got any further with this john?

 

!



High hydrocarbons is the clue - this is normally down to a poor ignition setup. I'd be fitting new plugs and making sure they're gapped correctly, clean the ignition leads, inside and outside of cap, rotor arm, etc and if any look suspect then replacing them.

 

Not had chance this weekend - busy working on my ABF'd mk2 try to get it ready to sell

Thanks for the reply paul - got some new plugs arriving from vwspares tomorrow, was hoping they'd be here for the weekend.

Will give the rest of the ignition a good going over while I'm at it - it's a H&H dizzy ignition setup, and only about 12 months old. I might borrow the leads off my mk2 and see if that makes any difference as well.

I'll update when i've had it back to the tester.

Cheers

 

Any update on this one? Thanks.

 

Hopefully going back for test tomorrow, bit's turned up from vwspares on Monday - just got them done tonight.

Oil and filter change with some forte flush slapped in for good measure.

New 4 point Beru plugs, checked leads looked to be in good condition. Gave the rotor arm and cap contacts a clean with some wet&dry.

Did seem to start up easier than it usually does, ran a bit better too - still needs to be properly sorted though - but hopefully enough to get through

One thing though - why does the rotor arm have a 5k Ohm resistance, surely the less resistance the better for a better spark?

Will keep you posted tomorrow.

Cheers

 

rotor arm

im not 100% sure but i think the resistor in the rotor arm is there to give it less wear. remove the resistor and it will spark for longer but would probably suffer more wear at the tips.

 

Finally got through the emissions test!!!

Took it to the garage tonight and stuck it on the tester - the initial readings were:

0.16% to 0.2% CO (very low) and 1400HC, and any slight increase in revs sent the HC and CO soaring. So the new plugs and service had brought the HC down from 2000 to 1400, but the CO level had dropped through the floor.

let it sit there and run for a bit longer while the emissions tester had managed to clear the HC out of it's system and was happy again.

Tried again but still no difference - was about to give up and go home when one of the guys pulled the filter socks off and sprayed a load of Forte carb cleaner down each trumpet and gave it a good revving. When the cleaner was squirted into carb No. 3 it really bogged down and spluttered but after a while it was ok again. Gave them all another good squirting and let the engine run for a bit to clear it out. Retested it.......

CO 1.3% HC 1130 - PASS!!!

They're gonna finish retesting tomorrow but at least the emissions are ok now - and all the other bit were easy to sort.

More follow up questions though:

What should the CO be at ideally for this - I recall the standard K-Jet is supposed to be 2%, is this the case for a bike carbed engine also?

Should the timing be set in the same way as in rubjonny's FAQ - i.e timing light onto flywheel through hole in gearbox?

I'm gonna have a good look at the carbs now the MOT should be sorted - what size should the jets be for a 1.9 motor, and where can I get some new ones if they're too big?


Cheers for all the help and advice - very much appreciated.

 

To help reduce the HC's, have you balanced your carbs?

Mine passed it's MOT today. With HC only 279ppm and CO 3.25% on R1 carbs.
I took it Bogg Brothers for a tune up yesterday. Before they balanced the carbs, HC's were 1300.

Emissions are now even lower than last years MOT when the car was on K-Jet!!
Previous K-Jet HC was 649ppm and CO 4%.

HTH


Lhasa2008

 

That's a bit of a concern if it reads CO 3.25% immediately after a tune up - ideally you should be able to achieve the same emissions readings as any other carburettor engined car, ie 1.5% +- 0.5%, which is also the manufacturer guideline figure for K-Jet.

Having said that, a pass is a pass.....

 

Not really, my engine runs too lean at the top end otherwise.
As long as the CO is less than 4.5% for a MK1 is a pass.

 

Haven't had them balanced yet - I have got a set of vac gauges from a guy at work, but not sure whether the carbs have vac connections on them - there is definitely nothing on the manifold runners. So not sure whether these will be any use or not? Will try to investigate.

I could take it to Boggys for a tune up, but I like to have a fiddle around with things and learn how they work etc - hence me asking all these questions, rather getting someone to sort it for me - I just like to learn (just bought a 4 gas analyser of fleabay so will get that hooked up when it arrives

Car is running at the mo - but it took MOT man 2 hours just to get it through the emissions test the second time around (very friendly place - didn't charge for a re-test). CO is still very low and HC just within limit at tickover, but skyrockets at the slightest touch of the throttle.

Runs ok when accelerating, but trying to cruise in traffic and it coughs and judders when you try to increase speed in high gear as though it's getting too much fuel (still popping on tickover too - though not as bad as before)

What jet sizes should the carbs have? What fuel pressure is best (currently 3psi) Any recommendations fot idle screw posistion (2 1/2 to 3 1/2 turns seems to be the usual rule of thumb)


Cheers

John

 

Jet sizes will depend on your engine spec, but I believe well mod'd 16v's usually have 180's (for comparision I have 175's in my 8v), but obviously it's better to start with smaller jet size first before you over drill the hole!

3psi is correct.


Lhasa2008

 

UPDATE......

It's been a while - too many things on the go as usual

Had a bit of an investigate tonight to see what is going on in the carbs..... Boggs allegedly serviced and checke the carbs when they built the manifold - though I'm uncertain to what extent they were serviced

Took the caps off the top of the carbs - not easy when some of the screws were badly chewed (mole grips came in handy though). Diaphrams looked to be in good nick with no perforations. One thing that was a bit dodgy were the small o-rings for the synchonisation port (example pic):

(Not my pic BTW)

Only one carb had a proper o-ring in - the other 3 had a piece of larger o-ring that had been cut up and bodged into the gap with superglue -- looked crap and wouldn't seal for toffee. I have temporarily replaced these with a small disc of rubber sheet to seal them up, as my carbs don't have a synchronistation port on the caps (yet ).

Checked the idle screws also - they were only 1/2 a turn out! This was due to trying to reduce the emissions - have set them back to 2 1/2 turns for the moment.

Checked the main jets also - when I eventually got the bottoms off the carbs, most screws were chewed up and solid (mole grips came in handy again) - not sure whether Boggs had them off or not due to the state of the screws. They've now been replaced with shiney new stainless cap head screws .

The main jets had a mixture of numbers stamped on them, 135, 130, 165, 160 (IIRC). But all of them had been drilled to 2mm! from what others have said this is a little on the large side for a 1.9 valver engine, ordering some new 175s from Allens tomorrow and get them fitted asap.

Will update on any more findings from the new jets etc.

Cheers

 

sounds like bogg bros have done a sh*t job or not touched them at all! the reason why they drill the jets to 2mm is just a ruff setting to get your car running in the hope you'l take it back to them for propper tuning. my 2.0 16v has been drilled to 1.75mm but im after some propper jets, are your carbs zx9r? if so let me know what the jets are like and how much they were as i want some!