Difficulty Starting And Cold Running

Evening all,

I picked up the bike yesterday, a 1979 T140E in generally great mechanical condition. It is a UK bike from new but was ordered with the Peanut Tank and High bars, like the US model. It has been uprated with nikasil-lined alloy barrels, Carillo con rods and pistons, balanced crank, updated push rods with Norman Hyde tappet adjusters, forged alloy push-rod tubes and Norman Hyde valve springs. There is an uprated oil pump and clutch, electronic ignition, 1.5 inch headers (no balance pipe) with straight-through Commando pea shooters (that sound fantastic). It has alloy rims with stainless spokes, Koni adjustable shocks, a 12 inch Norman Hyde front disk and fork brace. Other than that, it is a completely standard bike ;-) and a great base for my winter restoration plans.

However, whist the bike rides and stops very well, it is challenging to start and will not tickover when cold. Attempts at starting are most successful with the choke on between half and full, find compression stroke and kick it with a little throttle, but it may take a number of attempts before it finally goes and then I have to constantly blip the throttle or she dies. Once she is fully warmed up after a ride around the block (running really well / pulling very strongly and smoothly) she will settle on a lumpy idle. The LH exhaust firing cleanly on each ignition stroke but the RH exhaust firing sporadically (a bit like one of those old static engines you see being shown at steam fairs).

So, suspecting a carb / fuelling issue I have done the following:

• Remove the airbox sides.
• Cleaned and re-oiled the (rather dirty) air filters.
• Removed and cleaned the throttle idle position screws and fitted new O rings.
• Felt the slides to set the throttle idle position screws at the point where they just touch.
• Removed the air bleed screws, cleaned the hole / passage with spray carb cleaner.
• Fitted new O rings to the bleed screws, screwed them in all the way, them out 2.5 turns.
• Removed the (very slightly sooty) plugs, cleaned, gapped and refitted.

I screwed both idle screws in a couple of turns, set choke and kicked her over. As before it took quite a few attempts to get her started (trying various combos of choke / throttle / cursing) but once she was running, I set the idle screws to get a 1000rpm idle with no choke (she does not like running with choke at any temperature).

After a little trial and error, I settled on 3 turns air bleed (this was how she came originally) as she seemed to run best that way but there was no improvement in the sporadic RH cylinder firing. I took her on a run around the block but once she was warmed up the idle was now 2500rpm so I tweaked the idle screws down so she was at 1000rpm again but still lumpy and occasionally stalling. Presumably when she is cold I will not have an idle as before. So, all that work has done nothing, other than to show that the problem lies elsewhere.

Are any of you Meridian Twin experts able to help me identify what this could be please?

Thanks,
Ian

 

Thanks Taff. My bike is a T140E with Mk2 2930 Amals, so no tickling required. Have been looking at the Amal site, thanks for the advice.

 

Good plan, I hadn't thought of that. Will check compression too, as Wishbone suggests

 

I will strip the carbs, put them in my ultrasonic cleaner for a couple of hours and inspect everything before ordering any required bits from Amal. I was looking on their website and about to order a couple of major rebuild kits but I have to supply needle and jet sizes. Are the needles and jets marked for easy identification?

 

Interesting; my carbs don't seem to have a tickler, at least not like you find on Mk1 and Mk1.5 Amals. How do you tickle the Mk2 930s please? Maybe this is part of the issue.

 

Ok. So I pulled the RH carb from the bike and stripped it down. Here is a link to a picture of it:

https://www.amazon.co.uk/photos/share/sBVTs1itdryRqHMli0zuFcPQiWY3OsC7zFkZU4G5K5G

Comparing this to the exploded view in my workshop manual has me a little confused so I have a few questions, if that's ok:

1. On the main body there is a blanking screw where my manual says there should be an idle jet.

2. On the float bowl, I have removed the cold start jet (size 50). You can see this lying on the top, next to the deep passage it came from. At the back of the float bowl (centre, top) there is another jet (size 25) which is not shown in my manual at all. However, as it feeds up to a hole on the engine side of the slide in the main body, I am assuming this is the idle jet. Is this right?

Apart from the above; all of the jets and passageways appear to be clear. I have blasted through with carb cleaner and all seems well.

Here are the sizes:
Main jet = 220
Needle jet = 105
Cold start = 50
The not shown but probably idle jet = 25

Any thoughts please?
Thanks, Ian

 

Thanks All. I am going to refurb both carbs first, then check for voltage drop to the coils and EI. Will post back results.