build thread: 16v + cbr900 carbs + high compression

[yeayeayea]

Yesterday. Drove it around the block the day before actually. The white oil pressure sender is leaking oil out the top, a new one should be here today. Other than that, and being low on oil for said reason, it seems to have weathered winter unharmed.

[yeayeayea]

So I pulled the plugs because the car was still misfiring after a couple days of driving it. I found the #4 spark plug had a chunk of the porcelain missing. This was an old plug I threw in there a few months ago after breaking the porcelain on the previous spark plug.

Two plugs, both with broken porcelain, both #4 cylinder. Any ideas? Im thinking it may be carb related, maybe a lean run situation that is making the plug extra hot, but I am pretty much clueless right now.

[mudanddust]

can you post up good pics of the broken plugs and the plugs from the other three cylinders? also how many miles are on the motor, good and even compression?

[Jones84]

I dont think its a carb thing. I have had the same thing happen in my low comp ABA 16v turbo. It was #4 as well.

[yeayeayea]

I can post pics of the broken plugs. I cleaned the other plugs with the wire wheel on my bench grinder so looking at them wont help much. The car ran awesome before the first plug broke, I spent a whole day drag racing at Bug Out (made it to the semi finals, like 8 or 9 passes ) The plug broke that time on the ride home from bug out actually, while on the highway. When I got home, I swapped in an old plug, which has now failed. I posted on NGK's facebook, and they recommended a plug for me, problem is I have not found it locally yet.

[lilredcabby]

hey ma ur inbox is full and wont let me send any messages to you...clear up some space i have another question haha thanks.

[yeayeayea]

[mudanddust]

finally got my new motor in the wabbit today, hopefully get it buttoned up and try to fire it tomorrow

[pnavarro]

yeayeayea, I read the entire post but i didn't find how big you drilled the main jets for you cbr900 carbs... I read in this same post a drill bit sized at .178 but ... sounds to big to be correct...? Help?

[yeayeayea]

I believe it was 1.73mm, not .173 inches. .173 inches would be much too big.

At least that is what I wrote in the info for this video back when I was piecing it all together

[pnavarro]

I thought it might have been a bit much at .173, so 1.7... nice, thanks for the info!

[rysskii3]

What is done to the engine to run 173?

[yeayeayea]

What is done to the engine to run 173?

1.8 16v, decked head, 3angle valve job, autotech cams, eurosport cat delete header, tt exhaust, no cat.

[rysskii3]

1.8 16v, decked head, 3angle valve job, autotech cams, eurosport cat delete header, tt exhaust, no cat.

Hmm, I got very similar mods, with a few more little things, but I'm on 91 octane. I don't know of I should install the 170 or 175. And I got 2l

[yeayeayea]

I run 93 octane in mine. You also have R1 carbs where I have cbr900 carbs. I think yours are 40mm versus mine being 38mm. That said I would shoot for the 175's.

The mains were the only thing I changed on my carbs, I left all the other jets alone. I did play with needle heights to dial it in some.

[rysskii3]

I run 93 octane in mine. You also have R1 carbs where I have cbr900 carbs. I think yours are 40mm versus mine being 38mm. That said I would shoot for the 175's.

The mains were the only thing I changed on my carbs, I left all the other jets alone. I did play with needle heights to dial it in some.

hmm, maybe i should get some 180 and 185. i do have mild p&p and TT 4 to 1 catless header.

[bmwquick]

So how is it daily driving this?? Your dyno showed your HP and torq were slightly under stock until 5k rpm. I'm putting together an R1 carb setup but I'm afraid intown driving will suck, right?

I have a 9a with ported head and an exhaust. I'd like to see if I can hit vr6 150 whp with some cams and maybe a header. Shouldn't be impossible.

[yeayeayea]

Well I broke my ankle back on may 6th, so the car hasn't moved since. But I daily drove it for a couple years. No problems, no air filters, all year round.

[steveo27]

Hope ya feel better chief. And hope to see ya around

[bmwquick]

Well I broke my ankle back on may 6th, so the car hasn't moved since. But I daily drove it for a couple years. No problems, no air filters, all year round.

Sounds reliable. Ever left you stranded? I'd like to DD mine to work/school when I finish it.

[yeayeayea]

Hope ya feel better chief. And hope to see ya around

Long time no see steve, still got the 12v?

Sounds reliable. Ever left you stranded? I'd like to DD mine to work/school when I finish it.

The only carb related problem I have had was a broken throttle cable that was made from a bicycle brake cable. The new cable I have has been problem free.

Other than that, I have had two spark plugs, both on cyl4 break the porcelain. Also have had two oil pressure senders fail, the second one being a used one I got from a friend though. Only other problem was a radiator clog, the little vent line on the top of the rad was clogged, causing the radiator to get filled with steam vapor and overheat the car. Pretty tame for a 23 year old car that gets driven hard every time it is running.

[bmwquick]

so slightly more reliable than mine. You said you may be able to hit 150 whp with some finer tuning, do you think that's possible? I would be very happy if I could get mine in the 145-150 zone without going for crazy cams..

[yeayeayea]

so slightly more reliable than mine. You said you may be able to hit 150 whp with some finer tuning, do you think that's possible? I would be very happy if I could get mine in the 145-150 zone without going for crazy cams..

Im sure its possible. I literally have only played with needle heights for tuning. no syncing, no idle jet adjustments. But it runs well enough that I dont care to bother with it.

[OrangeDUB]

What throttle cable did you end up using? Last time I asked I think your reply was a bicycle cable, but I see that didn't last.

[yeayeayea]

So its time to make a new throttle cable, since my bicycle brake cable finally died.

I am using a honda hood release cable, as it has the right size barrel end for the cbr900 carbs


It has a barrel on one end and a ball on the other, i cut the ball off


next I cut the J hook off the stock cable, and drilled out the cable that was left crimped inside it


Here is what ends I will have once I determine my length


hopefully tomorrow I will cut it to the right length and crimp and solder the j hook on and have a nice new throttle cable with no cable clamps anywhere

I think it came out of an early 90's honda accord.

[OrangeDUB]

Thanks for the info. So did you get the Accord's steel cable to take the solder in? I can solder better than most and couldn't for the life of me get the OEM cable to take the solder, even with more than enough intense heat and plenty of flux.

[yeayeayea]

cant say for sure, but I think it flowed in ok, at least into the hook. I crimped it first, so it may be the crimp doing all the work.

[marcabrams]

with line is the main fuel line the top hose or the bottom

[OrangeDUB]

with line is the main fuel line the top hose or the bottom

The bottom is your fuel input. The upper 2 nipples that are between the carb pairs are your guel overflow/return, and the main big upper nipple in the center by the throttle cable attachment is a breather for the main venturi vacuum chambers, and that needs to breathe to atmospheric.

[yeayeayea]

Soon

[scirocconaut]

I would like to convert, wish I hadnt sold
My hayabusa carbs

[yeayeayea]

I wouldnt mind stepping up to some carbs with a larger Throttle plate diameter. the cbr900 carbs are 38mm, i think R1 carbs are 40. Do you know how big the busa carbs are?

[OrangeDUB]

Ever since I put carbs on my rabbit, I have since questioned why I didn't get hold of a digifant ECU with wiring and some injected motorcycle throttle bodies...

[yeayeayea]

Ever since I put carbs on my rabbit, I have since questioned why I didn't get hold of a digifant ECU with wiring and some injected motorcycle throttle bodies...

Well the carbs are a lot cheaper and simpler than going through all that hassle. But Fuel injected ITB's have a higher power potential if done right.

[yeayeayea]

Say what!?