hard starting

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Apr 15, 2004
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I'm frustrated. Am hoping for some good advice. My bike (750 with points, amals, stock airbox) starts first kick warm but is a real bear to start when cold. Sometimes it starts in a few kicks, sometimes it takes 15-20 kicks, other times (like today) it fires up and immediately fouls the plugs (with gas not oil).

It has a nice fat blue spark when I kick it over, the timing is good, the autoadvance seems to be working fine (according to my timing light), it has good compression - 140psi, and the jetting is pretty good now. When it does decide to run, it runs very well once warmed up.

So what could it be? Would installing a Boyer help? Should I get new amals or maybe a mikuni kit? I wouldn't mind spending the money if that would fix it but I hate to through good money after bad as my dad used to say.

One possible problem is PO removed the chokes and threw them away (yes, the hole in the carb tops are plugged). All I have to work with are the ticklers. It seems to start better in colder weather (today was about 70). Would replacing the chokes help? What do those of you with amals do to start in warm weather - ticklers, chokes, or both?

Oh and is there any way to clean the fouled plugs such as burning them off with a propane torch or something? Or do I have to just buy new plugs every time? At this rate I need to start buying plugs by the case :(

Hi Deb,

I laughed out loud when I read "fat blue spark". I love that description and can't wait to use it.

First, a Boyer ignition system will not cure this problem; your starting woes are carburetor related.

When you tickle the carburetors, you should stop at the first sign of gas seeping from around the plunger. If you get carried away tickling, the engine will flood with raw gas and become hard to start. However, if this should accidently happen, try starting the bike with the throttle full open.

Also, check to make sure your floats aren't sticking after tickling the carburetors. If gas continues to seep from around the plunger after you release it, the float is sticking.

You may want to check your pilot air screws; they should be about 1.5 turns out. Adjsuting the screws out increases the amount of air flow and makes the engine run leaner, adjsuting them in makes the engine run richer. If the bike starts fine when hot, then I doubt your pilot screws are set too rich, but check them anyway.

My AMALs have no chokes and starting cold is not a problem; so don't worry about the missing choke slides.

Spark plugs will sort of self-clean if the carburetion is correct.

Check the above and let us know the outcome.


What's wrong with Fat Blue Spark? I think it's descriptive. That's certainly better than a weak scrawny yellow spark, or so I've always been lead to believe :) I guess my point was I didn't think it was ignition-related either.

The air screws are 3/4 turn out. 1.5 turns out was too lean. And this is at mile-high Boulder. Perhaps the pilot jet passages in the carb are partially clogged? Could that have anything to do with the starting problems?

I have had a lot of trouble with sticking floats, usually right after putting the float bowls back on (something I've been doing a lot). Today they didn't seem to be sticking but I had to hold the ticklers down quite a long time before gas started overflowing. I wonder if it was filling up the cylinders instead of running out on the ground???

Your pilot srews are only 3/4 of a turn out? This is a curiously rich mixture.

The air at 5,000 feet is obviously not as dense as it is at sea level, resulting in a rich mixture on an engine/carb adjusted for sea level conditions. So, if anything your pilot screws should be about 2 turns out. This is about 1/2 turn leaner than a typical sea level adjustment, effectively compensating for the thin air at your higher altitude.

Something is wrong with your pilot/idle circuit. Your thoughts about a partially clogged pilot circuit may be relevant. But a clogged pilot circuit combined with pilot screws adjusted out only 3/4 of a turn is counter intuitive. But clean these passages anyway; you can use spray carb cleaner and compressed air for this. Better yet, soak the whole carb in cleaner.

Sticky floats will definitley cause all sorts of problems. Make sure the float bowl gasket is not interfering with the floats; this is about the only thing that can cause the float to stick. Also, make sure your float needles have rubber tips.

In addition, you may want to check your float height. To do this takes some fiddling. Install the float, pivot pin, float needle and gasket. Next, trap the float pivot pin by pressing down on the gasket on each side of the float with your fingers. Then carefully turn the whole mess upside down, making sure your fingers are not interferring with the float. The float should drop to a point where the edge of the float is aligned with the edge of the bowl. Under no circumstances should the edge of the float be below the edge of the bowl (viewed upside down); this will result in an overly rich mixture.

Are the carburetors relatively new? Perhaps they should be replaced. Typically, what wears out on AMALs (short for amalgamate) that requires replacement is the bore and throttle slide. If these parts aren't too sloppy and the engine idles smoothly, then your OK.

Let us know how you make out.

yeah, I think the carbys will need a good soaking. But I don't think that's my main problem right now.

I tried the bike again today. It started right up on the second kick and ran normally for a couple of mins. Then it died when I let it drop down to idle. It didn't restart right away but I eventually got it going again. This time I kept my hand on the throttle and kept it revved a bit. After a minute it abruptly died like I'd hit the kill button. Totally dead. That doesn't sound like carbys to me.

I now suspect the Lucas kill button has gone flaky on me. When I got the bike back in April I had to clean the contacts on the other switch cluster. High beam wasn't working. I didn't do this side though. My old 850 developed this exact same problem and stranded me in the middle of nowhere once. I disabled the kill button on that bike by soldering a jumper wire across the switch contacts. I just didn't trust it any more after it did that to me. I think I'll try that with this one and see what happens...

what's in a name?

amalgamate -> amal huh? Interesting. Is that a reference to the company name or to the pot metal they cast the things out of? :)

Amalgamate refers to the action of the carbutetor - the carburetor mixes or combines air and gas to make a whole fuel that can be burned by the engine. AMAL became the name of the company,

Well the kill switch would certainly be a convenient problem with an easy fix. Also, the ignition switch is often a source of intermittent problems. But doesn't this all fly in the face of that "nice fat blue spark"?

At any rate, checking the kill switch and ignition switch would be a next prudent move.

I would suspect the carbs. With your history of sticking floats, the engine dying could have been because you just ran the carb bowl out of fuel due to the float sticking closed. I'd thoroughly clean the carbs and consider sleeving or new carbs if the slides are badly worn. Don't forget the idle air screw passages.
Check your connections by temporarily running a new wire directly from the keyswitch to the coil (white wire). If this cures it then go back through the connections from coil to kill button to keyswitch. I would never permanently disable or bypass the kill switch. A stuck slide can get pretty exciting if you have to reach down to turn of the ignition at speed.
I also would recommend a Boyer or Rita (if you can find one). Much less trouble than points.
For the fouled plugs. If you have an air compressor, those little grit blasters sold by Harbor Freight and Eastwood do a pretty good job. I have used one for years.
Thanks, Ron. That sounds like good advice. I hadn't thought about the floats sticking closed. I did have to tickle again to get the thing restarted so that could be it. I've had so much trouble with those stupid carbs!

I removed the switch cluster and checked it with an ohm meter. Kill button is fine. One side of the turn signal switch isn't working but I don't have turn signals so I'm not too concerned about that right now. Guess I'll be spending some more time troubleshooting. Sigh.

Or maybe I should just give up and put a mikuni on the bike. I'm really getting tired of endless carb work.


After 17 years of goofing around with the stock carbs I finally gave in to a 34mm Mikuni this year. So far it's been great, maybe a little less top end now and the choke/fast idle seems to be too rich. The top end doesn't concern me and I think the choke is a jetting issue I'll work on. Starts 1st or 2nd kick, once it's warmed up it runs like a top. Very smooth, steady idle (read no stalling in traffic) as well as smooth pulling from 2k up. So far it's stayed in perfect sync. :wink: Highly recommend the electronic ignition as well, cures most of the hard starting woes.

Hi Deb,

Being a keep-it-stock kind of guy, I hate to see you throw in the towel and install a Mikuni. However, I can also understand your frustration.

If you go the Mikuni route, make sure you have clearance for the air filter. I've seen some people really scrunch up their air filter in order to get it to fit on a Mikuni equiped Commando.

I have dual Mikuni's on my '75 and stock, unsleeved Amal 932's on both the /73's. I have more problems with sticking floats with the Mikuni's than the Amals. Granted the cafe racer gets less running time than the Roadster or the Interstate, but if it sits for a week or more, I have to pull the float bowls and slides and clean the crap out of it. I had a friends 850 with single Mikuni in the shop to shim the clutch and he left it here for two weeks. Had to clean the carb to stop it from pi$$ing gas all over when he picked it up.
I'm not impressed with the Mikuni.

P.S. - both stock setups idle at 800 rpm or less. One has the original slides!
Yes, I want to keep mine stock too but we'll see...

I thought of something regarding those sticky floats. PO didn't believe in replacing gaskets, he just slopped gasket sealer on and kept using them. He used some goop like gasgacinch (sp?) on the float bowl gaskets. I thought I cleaned all that stuff off but maybe there's still some on the floats. If so, how can I clean them without melting them?

BTW the goop didn't stop the gas leaks but new gaskets did :)

The biggest worry would be the float needle. If it is plastic, throw it away. If it is the viton-tipped brass one you can clean it with lacquer thinner. As to the plastic float, you can try rubbing alcohol and perseverence. The metal spindle should be easy to clean.
Hi Deb,

Please excuse my ignorance but who is PO? Is it the name or abreviation of some old mechanic? Great spelling job on Gasgacinch, which is an old, old product used primarily to hold gaskets in place during assembly.


PO = Previous Owner. I picked up that term from another forum. It's a nice term, so succinct. I like it :D

I found a problem. I put the switch assy back on the bike tonight. When I did so I noticed the connector block the white lead plugs into is broken! The white kill button lead was just sitting in there loose, rattling around. So that's at least part of the problem. I tried to take one from the turn signal wires but both of those were broken also! PO had the wiring harness replaced a few years ago but his mechanic must have reused the old connector blocks. So I have some new ones on order from OldBritts. They stock them. In the meantime if I want to run the bike I have to take one from some other circuit I can live without, or run a jumper wire. Didn't have time for that tonight.

Don't know yet how sticky the floats are. I think I'll fix the wiring and see what happens. I do have the viton-tipped needles BTW. When I got the bike it had the cheesy nylon ones so I replaced them. It idled a lot better after doing that.

upward and onward,

Thanks for the PO answer; I figured it out after I sent the question to you and felt pretty stupid.

Keep after it; don't give in to those enticing Boyer/Mikuni gremlins yet!

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