Awesomly horrible rm100

[mxwannabe]

Well my rm100 is mechanically sound. minimal rust on frame and parts. Very clean engine, everything is great except freaking electronics :bang: I've cleaned all the grounds and have removed most rust from magneto, but my spark is still to weak to ingnite the gasoline. Does anyone have a wiring schematics for a 79rm100 if you do PLEASE post it. By the way is 135 psi good for a rm100. please post with somekind of help.
Is this bike worth keeping or should I sell it?

 

[TimberPig]

Have you gone over the bike and cleaned all the connections, not just the grounds? How is your plug wire and cap, if they are breaking down, they will increase resistanceand reduce spark output. NGK makes a cable splicer to attach a new wire if the wire is not intended to be replaced on your coil. It may be that your external coil or internal coil are breaking down and simply won't produce enough power to create a hot enough spark to fire it. Rarely the flywheel magnets lose strength and cause a loss of spark. I would go over the entire ignition system and check for dirty connections, chafed wires, or anything else that might cause a loss of spark, although it sounds like you have got a pretty good start on it. You can find microfiche pictures of the ignition and wiring at alpha-sports.com/suzuki_parts.htm

As to the compression, I'm not sure what the specification is for that engine, or if there is one, but it should still start and run at 135lbs.

I had a 78 RM 100 as my first bike 10 years ago. It was a decent machine, but didn't like to be jumped (my ankles still remember doing so) and mine would not lift the front wheel up no matter what I did. It was also fairly heavy, my 91 RM 125 was lighter and way more powerful. Popped the fuel line off at high rpm and lost the main bearings, let it cool and it would still run but needed to be rebuilt. I ended up getting hosed trading it for a pos snowmobile. I should have kept the bike and put a set of bearings into it.

 

[mxwannabe]

Well i bought a new spark blug ngk br83s or somthing along those lines and i bought some kind of spray to help it start up. So i put new plug and and hooked up the fuel lines and had my dad drag me for like 4 hundred yards. It would rev up really high but no explosions. so i took out plug and it was completly dry. So it turneds out that my problem is something with the fuel system. I just bought a brand new carboretur from vintage suzuki. It is a 79 rm125 carborator he said he would put stock jetting in for me so i have no clue what the problem is.
PLEASE PLEASE someone help me i have no idea what the problem is

 

[TimberPig]

First off, starting fluid is bad news in a 2 stroke engine, as it contains no lube. Since the oil mixed in the gas lubes a 2 stroke, you should use something with some lubricant in it, preferably fresh premix. You can trickle a teaspoon into the cylinder through the spark plug hole, and see if it fires on that. If it does, then dies, your fuel system is in need of some work.

If the plug is completely dry, you have a blockage somewhere. This may be as simple as the fuel valve is shut off, or it may be a dirty strainer in the tank, a plugged fuel line, stuck inlet needle, or a very dirty carb. I would suggest you pull the fuel line off the fuel valve, and try turning the gas on. If fuel comes out readily, your strainer is ok. then pull off the line from the carb and blow through it to ensure it is free. If that checks out, you will have to pull the carb and check it out. If the bike has sat a while, odds are decent it will need to be cleaned. If it is dirty but not absolutely disgusting, carb cleaner and compressed air should get it cleared out. If it is really gross, it may need to sit in a dunk tank of carb cleaner.

Why did you complicate things by getting another carb that may or may not have a problem with it as well? It is far easier and cheaper to try and fix the carb that is on the bike than to try and troubleshoot why it won't run when you are tossing other variables into the mix. I just looked, and the carb for a 79 RM 100 is not set up the same as a 79 RM 125, so that will only make your life even more difficult. I would recommend unless your carb that came on the bike is not usable (with a cleaning as needed) that you clean it and put it back on to make your life easier. You can view an exploded view of the carb, and the stock specs by going to Alpha-Sports

 

[mxwannabe]

well the origanal carb really is not usable the needle valve is bent. it looks almost exactly like the new mikuni except for a few things. I doubt that anything is wrong with the mikuni it is brand new never used. do you know the stock setting for my rm100. but ill take another look at the old carberator

 

[mxwannabe]

Wait a minute what do you mean by the fuel valve is off?

 

[TimberPig]

That needle could be replaced, it comes out and can easily be switched. It is actually changeable to adjust the air/fuel mix when jetting the bike.

The stock settings for the carb are available if you click on the RM 100 Carb Settings here . It was posted in my last message, but I guess you missed it.

The fuel line connects onto the fuel valve, as shown in this link Fuel Valve . If the valve is turned to the side, no fuel will flow it must be turned so the little lever is in line with the fuel line. I'm sorry to say it, but if that is all it is you are going to feel really silly :) . Don't worry, we've all been there before though.

 

[2stroke]

I assume youve had the plug out, resting on the head, while kicking it over? What does the spark look like? Fat and blue, or thready and weak?
Also, I second the premix down the spark plug hole....I would definitely slosh some down and replace the plug quickly and kick it.....if it pops over then the problem is fuel....

 

[2stroke]

Failing all else....start replacing ignition parts. Is that a CDI ignition or points? You can test coils with a multimeter, but then you have to know what good units should read.... unless you have one thats completely open then thats bad for sure. iF its points and they are not set right, that will give you a weak spark, but Im thinking its CDI....

 

[TimberPig]

It is a CDI ignition.

 

[mxwannabe]

Ya well I definatly had the fuel valve open. I though there might be another valve somewhere on the carb. Its not the needle that got bent. its the jet. I tried pooring some premix down but nothing happened. The gas is pretty old though. im pretty stuped at what it could be because i remove exhaust and there was gas inside it so im thinking its a spark problem. There is a new coil so thats not the problem. Its either the magneto or the cdi. I just praying its not the cdi cause a new one at alpha sports is 250 bucks.

 

[TimberPig]

Ya well I definatly had the fuel valve open. I though there might be another valve somewhere on the carb. Its not the needle that got bent. its the jet. I tried pooring some premix down but nothing happened. The gas is pretty old though. im pretty stuped at what it could be because i remove exhaust and there was gas inside it so im thinking its a spark problem. There is a new coil so thats not the problem. Its either the magneto or the cdi. I just praying its not the cdi cause a new one at alpha sports is 250 bucks.

The jet needle and needle jet can both be replaced.

Old gas is less flammable as the light ends that ignite easiest evaporate off. Fresh fuel will make a big difference.

Read this link Starting Bike and try checking the voltage output as described. it will soon tell you where the problem lies. Unfortunately ignition components are expensive as you have found out. If the flywheel magnets are weak, the stator windings or CDI are breaking down, or the connectors/pickups are dirty/rusty, they may not produce a strong enough spark to start and run.

 

[mxwannabe]

I dont know of any place where I can buy a replacement jet, alpha sports doesnt sell them and they are who i turn to for parts. All my connections and grounds are clean. There is one wire coming out of the coil that has nothing to connect to, im pretty sure its a ground. It is black with a white stripe. The spark coming from my bike is blue and pinkish. doesnt jump very far but it does jump alittle.

 

[TimberPig]

Have you tried calling Alpha Sports, or just looking online? They list the part number as no longer being in the database, but that just means Suzuki doesn't list it anymore. The part is still available for the carb through Mikuni, who actually made the carb.

Carb Parts Warehouse

or

Sudco

both have very large catalogs of carb parts, and can get the part you need. It is an R-4 needle jet, but you will need to know the series you need to get the correct part.

I believe the black with white tracer is normally a kill switch wire. it either connects to the kill switch directly, or through the CDI. If you got the right coil, you have got something disconnected or missing. The ignition system is normally open, which means the kill switch grounds the ignition system to kill the spark and shut the bike down, so with it open, you may still have spark, but your kill switch wouldn't work.

A thin blue spark is normally somewhat weak, particularly if there is some pink. Make sure your plug gap isn't too large.

A pipe full of gas could mean flooding, which will prevent starting. If the plug is dry though, you may not be getting fuel to the combustion chamber.

An engine needs the correct air fuel mix, adequate compression, and a strong enough spark at the right time to run. When any of these elements is missing or incorrect, you can experience difficulties in the running, or it will simply not start and run.