I previously found that having a random piece of carboard taped over the air box made things run but removing it caused the engine to bog down and die. I finally got around to doing the air/fuel adjustment yesterday and appear to have cocked something up
It's a CBR900RR in a kit car and, after a bunch of reading, it looked like I could wind each mixture adjustment screw gently to it's stop then out 2.5 turns. I did this and went for a drive, all was well.
After about 10 minutes, on the way home, the engine died. The fuel filter was empty so I think it did genuinely run out of fuel. 2x5L cans later and it fired up but wouldn't allow anything more than about 1500 RPM. I limped home and tested the fuel pump, all fine and pumping well. I re-set each adjuster to 2.5 turns, no change. I tried 3 turns, no change.
I removed each adjuster completely, all looked fairly clean, popped it all back together and now it's popping and banging and over revving but still won't take any load from the throttle.
Although I thought I was gentle seating each screw, my only guess is that I damaged something doing that but was after any thoughts/suggestions
Symptoms point to fuel starvation. Are you using the low pressure pump from e.g. an early CBR900RR or similar bike, or are you using a car fuel pump with a pressure regulator?
all the airlines ok, no leaks? no pinched pipes either? inmey rubbers all ok and carbs seated in them properly?
I had issue years back with my 98 rr.w and found it was a pinched breather to the carbs. I know you have more room in a kit car but worth starting with the basics
Sadly I don't think so, I had a good look around and no signs
I've got a tachometer coming so I'll adjust all the set screws to the full procedure and see if that helps but it feels like something's gone wrong with the fuel screw adjustment, I just don't know what
I previously found that having a random piece of carboard taped over the air box made things run but removing it caused the engine to bog down and die.
After about 10 minutes, on the way home, the engine died. The fuel filter was empty so I think it did genuinely run out of fuel.
If this was a bike, we'd know the sub-systems and be giving you the right answer immediately <honest :angel> .
- Do you have any photos that show your intake system with/without the cardboard?
- What elements are in your fuel supply line - from fuel tank to carbs?
Since everything was going well until you ran out of fuel, does this indicate that some rubbish has got into the carbs?
Whip one or more float bowls off and check? While you are in there make sure that the float needles are OK?
Can you check and make sure that the accelerator pedal is moving all 4 carb throttles?
Can you remove the air filter and make sure that the main jet sliders are moving freely?
And are they moving as expected with the throttles when the engine is running?
Might be worth taking the caps off and making sure that diaphragms (and jets) are OK?
It's exactly the same set up as the bike, they've just hacked the top of the airbox off because the bonnet wouldn't close and taped some card over it. Pic attached
Tank through flexi lines and a filter then to a 2-3 psi pump to the carbs. I have used the exact same set up before and it worked well (and has been so far)
I thought the same about pulling some muck in, I'll have a check in the carbs as soon as I can
All throttles are moving and I'm checking the jet sliders tomorrow all being well
It's exactly the same set up as the bike, they've just hacked the top of the airbox off because the bonnet wouldn't close and taped some card over it. Pic attached
Checked the timing this morning and it's bang on still (thankfully!)
Yes it's the stock air filter and not rejetted that I'm aware of
Just removed the cardboard, nothing else
Propshaft bolts straight onto the engine with a greased joint
Just fired it up again and still running like crap but after idling for a few minutes it cleared a bit and was revving a bit before bogging down and stalling. I left it a bit longer and could rev more and now I can get all the way through the rev range and it sounds fine.
So it's fixed itself. I guess something in the carbs?
I'll pop out for a drive and see what it does but I think I'll get a full carb rebuild kit next
However, just looked to get the above details - Search "CBR 900 Carb Kit" and there is a more comprehensive kit - additional parts include the fuel enrichment slider, trumpet seals and main jet holder&needle - at £39.99!?! But, I cannot vouch for the quality.
And, there is another company but the picture is quite small and I just cannot seem to make out what is in the kit.
I have had a couple like that in the past but they tend to get very wet!!
I've been a bit brave and gone for a Chinese carb kit after all because I liked the look of the extras, will take some pics when it arrives and see if that reveals anything. Expect lots of 'how do I rebuild this bit' questions to follow!
Well, a picture says a thousand words! I decided I wouldn't be comfortable just hoping it was OK so started stripping the carbs today. I found:
- A missing washer on a pilot screw
- 4 very badly damaged O rings to match on the pilots
- 2 large pieces of foam melting away inside the carbs (looks like part of an air filter)
- Bits of dirt in various places
- Assortment of jets with muck in them
It wants a good clean up and a bunch of new parts but I guess the foam was the biggest culprit and would most certainly have continued to plague me had I ignored it!
It's the only way for me I'm afraid, I do admire those guys who can pick up one of the 5000 different brass coloured pieces and know exactly where it goes but I need lots of cues! Fingers crossed the new rebuild kit will turn up soon and I cna get moving, will keep you posted!
The only ID I can see is "VP" "Kei Hin" "Japan" on the carbs
I think it's a 1993 893cc engine
Ian
The jet needle holder O ring is supplied so it's not that one I don't think
Pretty unimpressed with the Chinese set then
What makes the jet wrong? I can see the emulsion tube is a problem but thought I could use the original one cleaned up with the new jet (which seem to fit correctly)
Do you know if the choke needle comes out? It looks like it should but I don't want to damage it by removing incorrectly
Sorry for the confusion, it's one "kit" of 4 rebuild sets. Each one has 3 jets in
The original markings are 120 adn the new ones are 122 so I assume a bigger holes/richer mix?
1. The gaskets
2. The O ring on the jet needle holder
3. The jet needle spring
4. The slow jet
5. The main jet
6. The float valve
7. The float chamber drain
8. The choke spring
9. The mixture adjustment screw
10. The mixture adjustment screw spring
I can't use:
1. The SE valve (choke) because it's missing the end, I'll re-use the old ones
2. The needle jet holder for the main jet - It simply doesn't fit!
3. The jet needle on the vac assembly - because it sits too far down against the old one, re-use them
4. The small O ring on the mixture screw because it's missing
I'll assemble based on the above and know it could well be coming apart again!
That's the spirit! And, it is easier the second time and the third is a breeze! :thumb::thumb::thumb:
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