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Bike carbs issues on a Lada engine
beqa16v - 8/4/12 at 05:48 PM

First of all hello everybody.
I am from Georgia, Tbilisi, rebuilding the Estona 21 single seater which was originally designed in 80s.
They came with Lada 1600cc heavily modified engines. The engine which I have built has:
Lada 1600cc 8v
bike carbs from ZX750. 160 main jets
Estonia 21 exhaust 4-1
intake and exhaust channes ported
T-shaped lightened valves
3 angle valve seats
2mm shaved from the head (compression 10.5)
BMW M20 valve springs
weight leveled pistons
lightened and weight leveled connecting rods
lightweight flywheel
crankshaft balanced together with the flywheel

The video of the first warmup is here: http://www.youtube.com/watch?v=GL_UAJEoD68
Dont judge from this video as things have changed since then

Carbs are 38mm Keihins from Kawasaki ZX750R, not the latest model, i think they are pre 2003.
I am using a standard Lada mechanical fuel pump with a return valve which maintains constant 1.5psi pressure. I am monitoring the pressure live having the gauge hooked up.
Took carbs to a friend of mine who works on bikes. He checked the bowls, diaphragms etc and confirmed that carbs are in a good shape. He also set a float height. All jets are clean, i have carefully drilled the mains out with a 1.6mm drill. They should be around 162-165 now. Idle screws are 3.5 turns out.

How it worked in the begining, all observations are made on neutral:
The engine starts fine but needs a choke while cold
when worm, it does not idle properly and returns slowly to idle sometimes.
struggles at around 4000 and refuses to go further on neutral. Bogs by staying at that rpm
sometimes struggles to respond to throttle input.
used to backfire from carbs

After working on elimination of potential air leaks I have removed the spark plugs today and they were very black with some black gunk on them.
Cleaned them and put back on. On cold it was perfect. Under choke the engine was working at around 1200rpm very well without backfires from carbs (I did not rev it though). But after it warmed up it started to struggle. Tweaked the dizzy a little bit and got a good throttle response from idle but could not go past 4000 again. After around 10-15 minutes of working i turned the engine off, removed the plugs and they were already black. Cant understand whats causing this. The return seems to be doing its job. I have tested it by pumping the fuel by a lever on the pump. I hear the fuel flowing back to the tank as the gauge reaches 0.1 bar.

will121 - 8/4/12 at 06:05 PM

posilbly running to rich from plugs, need some sort of lamba mixture sencing to check, may be main jets to large as aroung 4000 rpm may be where the main jets start to effect mixture, as for tick over mixture try adjusting air screws 1/2 turn at a time to see what gives best idle running

[Edited on 8/4/12 by will121]

r1_pete - 8/4/12 at 06:20 PM

Also check the carb tops for leakage, I used to run the same carbs, to ensure a seal I filled the groove in the carb lip with rubber lube before seating the diaphragm.

beqa16v - 8/4/12 at 06:30 PM

quote:
Originally posted by r1_pete
Also check the carb tops for leakage, I used to run the same carbs, to ensure a seal I filled the groove in the carb lip with rubber lube before seating the diaphragm.

They dont have adjustable needles do they? What kind of washers should i put under them when tuning? How many mm?

snapper - 8/4/12 at 06:36 PM

Mikunies have white washers on the ends of the needle you can move them up to reduce mixture down to increase.
The needles have a profile and different profiles can increase ordecrease mixture at different revs.
There are also some good set ups available if you google Mikunie and Bike carbs

beqa16v - 8/4/12 at 06:39 PM

quote:
Originally posted by snapper
Mikunies have white washers on the ends of the needle you can move them up to reduce mixture down to increase.
The needles have a profile and different profiles can increase ordecrease mixture at different revs.
There are also some good set ups available if you google Mikunie and Bike carbs

Mine are Keihins. I have removed one needle and it does not seem to have shims for adjusting washers

jacko - 8/4/12 at 07:18 PM

It sounds like your carbs are like my zx9r E carbs where you put small thin washers under the needle top .
you say it will not rev past 4000rpm is it like its on choke ?
is may be that your jets are two big for a 1.6 engine especially as the plugs are getting black
the other thing is you really need a bike fuel pump there the best for bike carbs
Jacko

beqa16v - 8/4/12 at 07:57 PM

quote:
Originally posted by jacko
It sounds like your carbs are like my zx9r E carbs where you put small thin washers under the needle top .
you say it will not rev past 4000rpm is it like its on choke ?
is may be that your jets are two big for a 1.6 engine especially as the plugs are getting black
the other thing is you really need a bike fuel pump there the best for bike carbs
Jacko

How thick the washer should be to match one step on adjustable needles?
No I was trying to rev a warm engine without a choke

I was trying to avoid the bike pump as the chassis can not accommodate an alternator (this is a formula car) but i guess there is no other way.
I tired another return valve which kept 3psi at one point and it was even worse. Went back to what I have now (1.5psi).

austin man - 8/4/12 at 08:06 PM

is the choke releasing correctly? and are you sure the butterflies are opening fully? I have ZX9 carbs fitted and the revs do seem slow to drop off

beqa16v - 8/4/12 at 08:08 PM

quote:
Originally posted by austin man
is the choke releasing correctly? and are you sure the butterflies are opening fully? I have ZX9 carbs fitted and the revs do seem slow to drop off

choke is fine but i think the throttle spring is not enough. Will add another one

beqa16v - 9/4/12 at 09:56 AM

quote:
Originally posted by jacko
It sounds like your carbs are like my zx9r E carbs where you put small thin washers under the needle top .
you say it will not rev past 4000rpm is it like its on choke ?
is may be that your jets are two big for a 1.6 engine especially as the plugs are getting black
the other thing is you really need a bike fuel pump there the best for bike carbs
Jacko

Oh and forgot to mention that it used to do the same at 2500-3000 the day before i removed plugs and cleaned them. Tweaking ignition was helping a bit but not much. Does this mean that the issue is spark related?

And another thing is that the engine ran rougher on a 3psi return valve compared to 1.5psi which i have now. Is it possible that even now its too much? Therefore can we assume that a bike pump can fix this issue?

jacko - 9/4/12 at 01:09 PM

quote:
Originally posted by beqa16v
quote:
Originally posted by jacko
It sounds like your carbs are like my zx9r E carbs where you put small thin washers under the needle top .
you say it will not rev past 4000rpm is it like its on choke ?
is may be that your jets are two big for a 1.6 engine especially as the plugs are getting black
the other thing is you really need a bike fuel pump there the best for bike carbs
Jacko

Oh and forgot to mention that it used to do the same at 2500-3000 the day before i removed plugs and cleaned them. Tweaking ignition was helping a bit but not much. Does this mean that the issue is spark related?

And another thing is that the engine ran rougher on a 3psi return valve compared to 1.5psi which i have now. Is it possible that even now its too much? Therefore can we assume that a bike pump can fix this issue?

What i was asking is when it bogs down at 4000rpm is it as if you have put the choke on ? I think you are running to rich = to big jets if so you will not need washers under the needle heads

I know from reading on here for years that not using a bike fuel pump that it can cause all kinds of problems can you try one to see if it helps solve the problem you are having

This is only my opinion and the best way it get it right is to have it set up on a rolling road
Mind you don't run the engine too weak and melt pistons etc
Jacko

matt_gsxr - 9/4/12 at 01:34 PM

This page is nice for explaining the complexities of how to tune these carbs.
http://www.factorypro.com/tech/carbtune,CV,high_rpm_engines.html

One important thing to recognise is that the low speed and the high speed are controlled by completely different parts of the carb. So you must adjust them independently.


If I were to guess then I'd say that the mains jets are far too big (or needles much too high), further you need to open up the idle screws to help at low RPM.


It might not be the fuel pump, but a bike fuel pump draws only 2A, so you can use one on a total loss electrical system with no real problems and you then can be sure that it isn't that.

beqa16v - 9/4/12 at 01:53 PM

Honestly I dont know how the choke bogs the engine. Never had a car with a carb. injection, turbos, rotaries - yes, but not a single carbed vehicle.
I agree with all the above points. Its already decided to run a bike pump. I will fit it to exclude that part of the puzzle.
I have an access to dyno but i want to make the car just run properly at low-mid rpms to break in the fresh rebuilt engine. After its done Ill proceed to precise tuning on a dyno (rolling road).

[Edited on 9/4/12 by beqa16v]

beqa16v - 13/4/12 at 01:42 PM

Took the carbs to a bike carb specialist. He disassembled them and they were full with mud. Dont even know how it got there. Needle on one of the bowls was not working and was changed. Will try to fire up the car tomorrow

beqa16v - 18/4/12 at 07:57 PM

popping and bogging at 4000 was caused by low fuel pressure (hence lean mixture). Discovered that by fitting a stronger return valve which maintains 3psi instead of 1.5. The engine improved immediately. Confirms the necessity of a bike pump. It will deliver right amount of fuel at any rpm.

But i have a lot of fuel in my oil. It smells fuel a lot.

[Edited on 18/4/12 by beqa16v]

[Edited on 18/4/12 by beqa16v]

jacko - 18/4/12 at 08:30 PM

Nice to know you found the problem let use know how you get on
Jacko

beqa16v - 19/4/12 at 06:04 AM

quote:
Originally posted by jacko
Nice to know you found the problem let use know how you get on
Jacko

Well yeah nice to find the reason at last. I think the fuel is still not enough at high rpms, the engine should be stronger still (i was only reving it on idle). Will try to get my hands on a bike pump. They are so hard to get here

beqa16v - 25/4/12 at 08:05 PM

Just bought a ZX6 fuel pump from ebay. Does it need a relay or I can just connect the wires and forget about it? I read somewhere that it needs a separate relay to stop pumping when unnecessary

ReMan - 25/4/12 at 09:08 PM

quote:
Originally posted by beqa16v
Just bought a ZX6 fuel pump from ebay. Does it need a relay or I can just connect the wires and forget about it? I read somewhere that it needs a separate relay to stop pumping when unnecessary


You dont need one for normal operation.
The relays are usually used to provide forced cut off in the case of some falure or stuation
Get it running without and add in later if you really feel the need

beqa16v - 25/4/12 at 09:19 PM

quote:
Originally posted by ReMan
quote:
Originally posted by beqa16v
Just bought a ZX6 fuel pump from ebay. Does it need a relay or I can just connect the wires and forget about it? I read somewhere that it needs a separate relay to stop pumping when unnecessary


You dont need one for normal operation.
The relays are usually used to provide forced cut off in the case of some falure or stuation
Get it running without and add in later if you really feel the need


Thanks a lot
A guy on another forum confused me by saying that I should know what kind of carbs I have to match the pump (get either electrical or vacuum pump)

My zx6 pump looks like this


Carbs are from a 750 and look like this


Hope I did everything right

ReMan - 25/4/12 at 09:48 PM

Another forum? I thought there was only one..
That should be fine. It has it's own internal regulation and only pumps as neccesary

beqa16v - 26/4/12 at 07:05 AM

quote:
Originally posted by ReMan
Another forum? I thought there was only one..
That should be fine. It has it's own internal regulation and only pumps as neccesary

Thanks a lot. I was already thinking I have missed something while researching on these.
The guy has exactly the same pump and he said it started to overflow as soon as he turned it on. Had to connect a relay etc. Cant see why this happened if the pump was working well. If the needles had problems then the relay should not have fixed it. strange

beqa16v - 6/5/12 at 07:12 AM

The ZX6R fuel pump has arrived. will pick it up tomorrow. any instructions before I install it? Does the pup say where the negative and positive should be connected? Will it be damaged if I mess those up? Any other tips?
PS. I have the engine in the rear so the pump will be close to both engine and the tank.

whitestu - 6/5/12 at 09:00 AM

quote:

Does the pup say where the negative and positive should be connected? Will it be damaged if I mess those up?


Hi

It should look like this:

[img] Description
Description [/img]



The wires to the connector are black and red. Red is live.

The one with the filter on is the fuel inlet.

They are best placed under the tank so gravity primes the pump.

Stu

beqa16v - 7/5/12 at 05:23 PM

OK fitted the pump and it works fine. The throttle response improved, its now perfect on a wormed up engine. The engine needs much less choke to work on cold as well. Return to idle is good also.
I still have to drive the car to see how it goes but I think this was the right way to go. The oil did not smell fuel as well. So yeah, looks like at least most of my problems are gone with the installation of the bike pump.

Thing that is not right is that the idle increases as the engine warms up. It reaches about 1200 at 80 degrees Celsius. Also it falls too low after return from revving and than gradually builds up. Any ideas in this regard?

beqa16v - 11/5/12 at 05:58 PM

here is a video from the startup
http://www.youtube.com/watch?v=OEBciIaQ4Jo

jacko - 11/5/12 at 06:36 PM

Are the slides in the carbs nice and smooth sliding up and down ? not sticking
Jacko

jacko - 11/5/12 at 06:42 PM

Iv seen the video but do you have any photos of your car we can look at ? it look very interesting
Jacko
By the way if it was me i would have the same length trumpets on all 4 carbs it should will make a difference

[Edited on 11/5/12 by jacko]

beqa16v - 11/5/12 at 06:56 PM

quote:
Originally posted by jacko
Iv seen the video but do you have any photos of your car we can look at ? it look very interesting
Jacko
By the way if it was me i would have the same length trumpets on all 4 carbs it should will make a difference

[Edited on 11/5/12 by jacko]


The slides are fine. They all move up and return freely. They respond to engine revs well from what i could observe. Can this idle issue be an air leak?
Yes the trumpets should be of equal length. These ones came with carbs so I did not have much of a choice.
At the moment we are restoring the original fiber glass body kit. The car utilizes ground effect and therefore has quite complicated sidepods.

The inspiration for Estonia 21 was Lotus 79 ground effect car. Actualy E21 has exactly the same rear suspension design. If you compare the pictures they are identical (other than lotus being much better built).

This is how it looked when I bought it. No engine, no radiators, pedals, front calipers and a lot of other things. Many parts were custom built



if you go through this thread you will find many pics of the car http://www.lada-vfts.ru/forum/index.php?showtopic=6380&st=0


[Edited on 11/5/12 by beqa16v]

[Edited on 11/5/12 by beqa16v]

[Edited on 11/5/12 by beqa16v]

[Edited on 11/5/12 by beqa16v]

jacko - 12/5/12 at 04:03 PM

Nice car and a great project keep us informed how you get on with the carbs and also the car
Jacko

beqa16v - 21/5/12 at 06:47 AM

quote:
Originally posted by jacko
Nice car and a great project keep us informed how you get on with the carbs and also the car
Jacko


Thanks. Have not started the car since then, we are dealing with the bodykit at the moment. It needs some restoration and painting.

[Edited on 21/5/12 by beqa16v]

beqa16v - 10/6/12 at 06:32 AM

Hi Again guys. Needles in sliders have free play. The move up and down inside sliders at quite some extent. Is this normal or are my carbs missing some parts?

beqa16v - 19/7/12 at 06:34 AM

Installed a racing camshaft which I was offered for quite cheap. The owner did not know the exact specs but after some measurements we came up to the following conclusions: around 315deg; intake lift 11.4; exhaust lift 10.8.
It turned out to be a quite wicked cam, the car wont idle with this cam even with the choke on. It simply dies straight away not even stumbling. On a stock cam the idle was fine though. The idle screws were 2.5 turns out.
I have resolved the issue with bogging at 4000 by blocking main and pilot air jets, the car revs all the way to stratosphere without any bogging).

Then took a car to a hill climb event just to test it. However I could not even run properly as the flywheel bolts broke leaving the flywheel detached from the engine. It is fixed now.

The question here is, how should I make this cam idle at least at 1500? I have turned the air screws and they are 4 turns out now, however I have not started the engine yet.
I have 160 main jets on these 38mm Keihin E carbs and two 0.5 millimeter washers under needles. Do 160 mains sound safe for the cam given the displacement of the engine is 1600 cc?

pics from the hill climb





video of the test run. It was in third gear
http://www.youtube.com/watch?feature=player_embedded&v=spWsA_0YTfk

[Edited on 19/7/12 by beqa16v]

beqa16v - 21/7/12 at 09:55 PM

Here are today's vids guys
Removed washers from under needles because the sparks were terribly black. After some running the electrodes became brown but their surrounding is still black

http://www.youtube.com/watch?v=lcsE5_BqHbQ

http://www.youtube.com/watch?v=gH4RoFV-NpU

[Edited on 21/7/12 by beqa16v]

beqa16v - 14/10/12 at 06:39 PM

hi again guys
some news concerning my car:
took it to the track, it was awsome. Its so sharp and grippy even without proper toe and camber settings. Its a bit hard to be precise during downshifts as you have to simply find gears which makes corner entry a bit tricky to manage. Its also hard to spot those entry points as well but i loved the exits when you keep constantly adjusting the steering wheel to keep it pointing the right direction.

Issues with carbs were solved by blocking the air jets but with 160 mains it is quite rich. It pulls without any popping in first and second but from 5000rpm in fourth and sometimes even in third at top rpms it is popping from the exhaust and loosing acceleration. Is it really rich mixture symptom? Doesnt engine require more fuel at higher gears? It should get better if its rich right? Are 160s too big for blocked air jets?

Also 4th carb is richer than the other three. Can it be syncronization related, or something else?

Carbs are 38mm Keihins and the engine is 1600cc 8V counter flow with ported head, headers and 315degree cam. 11.5/10.8 lift.

[Edited on 14/10/12 by beqa16v]

beqa16v - 15/5/13 at 11:10 AM

Ok guys here is a video of me driving on a skidpad. It was fun. The car is very nimble and quick
http://www.youtube.com/watch?v=jYNGXbq3xS0

mark chandler - 15/5/13 at 12:21 PM

Loving the way you can test your car in a public car park, I cannot see any of us getting away with that in England !

What gearbox are you using?

beqa16v - 15/5/13 at 04:02 PM

Well its not a public car park. Its a race track skid pad. Main straight is behind those buildings on the left.
The gearbox is a dog box with straight cut gears. It was based on a gearbox from this car:
Probably designing a racing gearbox from the scratch was too expensive for them in USSR.


[Edited on 15/5/13 by beqa16v]

DarrenW - 15/5/13 at 05:34 PM

quote:
Originally posted by r1_pete
Also check the carb tops for leakage, I used to run the same carbs, to ensure a seal I filled the groove in the carb lip with rubber lube before seating the diaphragm.



Ditto. I had carb top leak issues, rubber lube worked a treat to hold the seal in place then help it seal when tops are screwed down.

After that basic checks at first to make sure floats are same height, needles are in same position etc etc. Once its running better you can then look at jet sizes etc. i was lucky and found a local expert to set mine up, Dave at Boggs.