Forum

[Paulk]

Jacob,

Glad you found a way to get it started. My only point was that opening the throttle effecftively renders the fuel enrichener useless because air will be drawn to the motor by the path of least resistance ie thru the carb main boby and bypassing the cold start system.


Again forgive me if I'm telling you stuff you already know but please don't draw conclusions from your past experiences with mark 1's when it comes to cold starting they work in very different ways. Does your MK2 have a cable or lever for cold starting? If it's a cable it works in the opposite way to a MK1 ie pull on the cable to activate.

When you've got the motor running and the cold start system in use you should have a fast tick over (even racing) without touching the throtle if not you should suspect a fault or using it the wrong way round.

[Alan R]

Hi guys, ----------- a few years ago I ran a 1970's Triumph 750 T140E Bonneville with a pair of Amal Mk2 Concentrics fitted. One major item I found was the the small rubber tip on the choke plunger would not seat properly or was worn/breaking-up. Just a thought-----------.

[JTL]

Paulk, since I'm not an expert, I'm happy to hear about all the little tricks for tuning carbs.

Both MK1's at my old Bonneville had no cold start system in them (removed?); at least there were no cable operated thing going on. Just press the ticklers till petrol was flowing, a twist on the throttle grib when kicking and the bike would start.

The MK2 for my Bullet has a lever on it. The bike will not start if I press the lever down (= opening the cold start system). Maybe the 50 pilot jet in the cold start system is too big? But if I twist the throttle just at the right time and the right amount when kicking the engine starts. Then I leave the throttle untouched and it has a fast tick over for some 30 seconds before revs are going down. Maybe I have just adopted an "uncorrect" way of starting the bike because this was the only way I could do it, or maybe the cold start system is faulty. I don't know what is right or wrong if there is any right or wrong to this. The bike starts and I'm happy.

AlanR, the rubber tip on the cold start plunger is new, so I presume it is sealing correct. I guess I need to do some testing to be sure, and to learn how the engine reacts to an activated cold start system.

Tomorrow I will try out a new combination of jets and slide. The mixture simply has to be leaner. I'll let you know about my results. Tips are still very welcome.

all the best
Jacob

[Paulk]

Jacob,
It would seem that that your cold start system is operating since you get a fast a tickover on start up and the fact that its slows down after 30 seconds suggests it get too rich quickly as the motor warms up.
I had a Commando with a MK2 fitted and all I had to do was switch on and jump on the kick starter and it would happily start with a fast tickover and get faster as the motor warmed until I knocked off the enrichner.
Since the bike is starting I would leave any fiddling with the cold start system until you have the rest of the carb set up since changes to that could well have knock on changes to starting.
My previous comments my have been off mark a bit since on looking for tuning notes on the MK2 they say don't open the throttle more than a quarter whilst starting so what work works right! There's a few notes out on the web and the ones I've seen are all similar to http://www.hitchcocksmotorcycles.com/hi ... concentric
Good luck,
Paul.

[JTL]

Paulk, I just had a short trip on the highway yesterday. The new set up is: 3,5 slide, 25 pilot jet jet, 106 needle jet, needle is second top groove and 190 main jet. Started fine with sort of high revs, but slowed down to "normal" quickly. At high speeds it's like the power at the wheel sometimes disappear and comes back on. Accelerating is slow. All this would indicate a rich mixture, so I have to try something leaner. The MK2 has a velocity stack on it and the exhaust is very free flowing. As mentined earlier the head is the tuned head from our host. Jacob

[Bullet Whisperer]

Hi JTL, I am with Paul K on the cold start for the MK II. If you have a 190 main jet in a 30 mm MK II for a partially tuned 500,you don't want anything smaller [you say you want to try something leaner], as you might harm the engine. I recently dyno tested a 500 which I had tuned. This machine had standard cams, but I ported the head, lightened the crank and shortened the barrel for 8.5:1 compression, the 32mm MK II Amal started off with a 270 main jet, but this was reduced to 230 for perfect fuelling according to the Dynojet Dyno. We eventually saw over 24 bhp at the rear wheel, as opposed to just over 21 bhp when we started off with the 270 jet and began working down from that size.
Have you checked your float height and fuel flow? Paul.

[Paulk]

BW, you beat me to it with fuel flow and flooding (not at the same time). I was thinking down the route of very over rich at tickover - since it slows down quickly after starting.

Jacob, BW is way more experienced than I at this stuff so ignore his advice at your peril.

I would start as per the tuning notes and get the pilot jet (actually air screw) set up right first. It's quite difficult trying to advise someone when you've no idea how competent they are you either miss out stuff they need to to know or you insult their ingeligence. That said, do to have the tuning notes and do you undersatnd them? Most people I know are completely lost when it comes to setting the tickover/air screw and are quite happy if it just ticks over with no understanding how it effects the rest of the range - not putting you there - - - yet.

[JTL]

Hi Paulk and BW

My fuel flow is good, but I have to check to be certain. My float is of an unajustable kind (white plasic), so the float height can't be altered unless I get another float.

I had a test ride Friday with the 190 main jet and the needle in the top groove; the slide is a 3,5. I also advanced the timing just a little bit. All of this improved performance (the feeling of a smooth ride and nice power pick up). But my spark plug still gets very black very quickly (brand new plug gets all black in 15 km). I start to get a feeling that something else than fuel mixture (jetting) is the issue here.


The bike starts easily, so I don't really need to use the cold start system. With the above setting the revs are not as high as before when starting and much sooner they goes down to a nice tick over even in this cold wheather. The tick over screw is 1 and a half turn out. I do have the tuning manual, but I can't say I understand it and I can say I understand it at the same. It's the dilemma you mentioned, Paulk, since I'm not a trained mechanic all I know is something I have learned from personal experience and good advice from guys like you at variuos Bullet fora. So I can't say I fully understand/know what is going on, but at the same time I do understand the simple mechanics of the Bullet, and also I'm able to repair it. Because of this no kind of advice even if I know about the stuff in advance will insult my inteligience. I'm too willing to learn to get insulted, so let all the good advice flow this way, Paulk, I'm all ears.

The riding season has come to an end here in Denmark, so all the fine tunig and testing will have to wait untill spring.


Thank you all for advice and tips.

Godspeed
Jacob

[Paulk]

Jacob,
So you’re running rich - as I said I suspect you are running very rich at the tickover/low end. Being able to start without cold start also implies rich. I would suggest (once the bike is warm) you adjust the pilot air screw (probably out), this should cause the tickover to get faster, then lower tickover with the throttle stop. Re-adjust air screw (in or out) to see if you can get the tickover to rise and again drop the tickover with the throttle stop. Keep going until moving the air screw in or out causes the tickover to drop - you now have the air screw in the right place and adjust your final tickover speed with the throttle stop. You are aiming to get the tickover as fast as possible with the air screw and set tickover speed with the throttle stop. One and a half turns out is only a starting place for adjustment. As the tuning notes say if you end up massively away from 1.5 turns out you should replace the pilot jet as appropriate but anywhere between 0.5 and 2.5 turns out should be OK. Good news for setting up pilot air screw/tickover is you don't have to ride anywhere.
All the best, Paul.