I've just about got my Blackbird 7 going - have been for a few short but exciting drives (can't go too far as not certified, registered etc yet) but I have some questions/issues.

1. Speedo not working - been using the Honda sensor to an Acewell speedo. Was working but now not. Not getting any pulses from the sensor, so I assumed it was faulty. Got another sensor (2nd hand but supposedly good) same result - no pulses from sensor. +12 and gnd OK. Either I've got 2 faulty sensors or there's something else. Ideas? Given the number of Blackbirds that have died in the UK there must be a surfeit of sensors available - anyone got one (known good) they'd like to sell me?

2. Motor not running very well under acceleration. Starts, idles etc very well but under load will hesitate/cough/splutter. Honda service manual suggests these symptoms mean the mixture is too lean (Carb'd engine). As I'm not using standard air box (using sock filters) and freeflow exhaust, I would agree that the mixture is probably too lean. On the Bike Honda run different jets in 1&4 and 2&3, also different length trumpets - is this because of the way the airbox affects airflow? Would it be better to now have the same size jets in all 4 carbs? and same length trumpets? any help appreciated

3. Before I get too serious with the car, I'm going to have to do something re dry sumping or other alternative. I have the standard sump (not chopped) which does mean the engine doesn't fit within the bounds of the body (sump 100mm from ground - carbs protruding through top of bonnet). What options are available?

Thanks

David

Hi David,

I'm not too clued up on the Honda speed Speed sensor or where it's mounted, but if it's giving you that much grief the acewell should run off a standard proximity/magnet setup.

You are without a doubt running extremely lean if you have binned the airbox and replaced with filter socks. A dynojet kit (with a rolling road session too if possible) will sort this out. I'm not too sure on trumpet lengths being different, but in a car install I would of thought all jets/needles would be the same & trumpets would ideally be the same length.

[Edited on 11/9/12 by Proby]

Having all the jets and trumpets the same size was my original gut feeling as well - this will be what I'll do.
I'm getting hold of an experienced bike tuner to have a look at my setup and to tune it.

I have the original Acewell sensor but if I can use (and I have had it working) the Honda sensor, this would be my preference. I suspect that both of the sensors I have are dead - can't see what could possibly go wrong with the gear that it senses to generate the pulse, hence my request for another known good sensor.

Whilst asking about Honda Blackbird parts - anyone got 2 spare longer trumpets for a carb'ed Blackbird?

Thanks

David

IIRC the trumpets are different lengths to help widen the torque band a little. The jets are different partly for this reason, and partly because the middle two cylinders run hotter so are jetted slightly richer. Keeping the different trumpets is fine, but a dynojet kit will be needed to let it run up properly.

As for it fitting inside the body work, I gave up with mine and just used the standard air box sticking through the bonnet with a K&N filter as that was the most straightforward option. But I only ran mine with a baffle plate so still had the standard sump.

Thanks for the reply DIY Si

I've been speaking with bike tuners and they also suggested the same reasons for having different trumpet lengths (and jet sizes)
I've got a Dynojet kit on order now.

I'm curious about the sump. I too have a standard sump (which I will be getting a baffle plate for). I asked the question once before about if the people who had had trouble with bearings were using standard or shortened sumps (without many replies)

Are you saying that with a standard sump you can get away with just a baffle plate? Is this on the track as well? I was looking to also also add an accusump unit for added reassurance as dry sumping is quite expensive.

As you can see by my avatar, the carbs and sock filters protrude above the bonnet line - I may yet make a 'bulge' to cover these but in the mean time I do quite like the look.

David

I don't have a blackbird engine in my car and I never have.

But I have so many threads that talk about No 3 bearing failure of the blackbird engine.

If you search on the terms "blackbird engine failure" you get 15 hits. I'd read them all if I were you so as to make sure that you don't make it thread 16.

Matt

I have seen most of those threads.
I acquired the Blackbird engine before I was aware of the No3 bearing failure issue.
What I want to know is - In the cases where there has been a failure, were they using a shortened sump?
By keeping the standard sump and using a baffle plate - will that be sufficient. I doubt I'll ever be using racing rubber, just decent road tyres. It may sound odd, but I'll be mostly using the car on the road with the very occasional hill-climb or track day.

David

I will happily admit that I blew my first engine up by not realising how important oil level is with a bike engine. I'm used to old A series lumps where you can run so low on oil the rockers squeak and not do too much damage. Once I had discovered this, I always ran with the oil overfilled by 1/2 pint/250ml and the baffle plate and I never even saw the pressure gauge drop or flutter. I always kept a litre bottle of oil in the car just in case of emergencies.

I never made it to a track, so I can't say how well it would stand up to continued track use. It never failed me on the twisty back roads where I had been known to use all the cars abilities though.