Motor won't start anymore

[Ritchie]

The motor was running fine before I cleanded the carbs. I also put in new jets.
I looked at the spark plugs and the give a weak spark. The battery is fully charged.

I am running out of ideas. Pls help.

 

[peanut]

Richie why don't you start by telling us what model year your bike is. is it standard or modified ?What carbs are fitted, Why did you fit new jets ? are they the same jets or differant sizes? Have you fitted electronic ignition ? Do you have an electric stater fitted ? does it work ?
What exactly you have tried so far.
What happens when you try to start the engine ?
You cannot expect us to guess all this

 

[Ritchie]

Hi Peanut,

You are right. It is the 1979 model with contact points. It has the BS38 carbs with open filters. The engine has open pipes. The jets are the same size.
Before I cleaned the carbs the engine was running a but rough, but no starting problems.
I replaced the jets for newer ones.
I checked the fuel line. No problems there.
I checked the sparkplugs. Very weak spark even with full battery.
I check the contact points, and found out that these ware out op spec. So I corected the,
I checked the wiring. No problems there......... until yesterday..

The right cyllinder gave an bang but the left not. Lest sparkplus was wet, right not.
Then I discovered that the wire to the Bobine or ingnition coil (I hope it is a English word) was broken.

I was going nuts because I had it running, but the battery was dead. So I figured, Charge the battery, and go.
I will do the following. Repair the broken wire. Replace spakplugs and contact points.

 

[peanut]

Ritchie the 79 model is the best model in my opinion....... probably because I have a 79 too

Now we know that your bike is standard and unmodified that should help a lot with diagnosing the problem.

It sounds to me like you are going to need to go through the whole bike systematically checking and testing everything because it is clear it was not running properly even before you cleaned the carbs "Before I cleaned the carbs the engine was running a but rough"

If you have a good battery and the starter motor is working then that will turn the engine over quickly and should help you test-start the bike. If the battery is not holding a good charge then use a car battery with jump leads ,it will give your battery a big boost . You need a fully charged battery to generate a good strong spark.

Check your battery earth wire and clean the chassis connection. Make sure that you have a good strong spark to both cylinders before you mess with anything else.

The more things you fiddle with the more problems you can accidentally introduce . Just tackle one thing at a time. Fit some new spark plugs and remake the HT lead connections to the spark plug caps and coils .
Then you will need to check both your points gaps and test both the capacitors/condensors. Also check that the advance is moving freely and is not stuck
See if that improves your spark first.

 

[Ritchie]

Hello Peanut,

I fixed the broken wire. It runs now. I will replace the sprakplugs later on.
On cylinder is giving a good bang the other not.
It will also rev up suddenly and then I have to cut power.
It will also rev up when I give it little more on the throttle.
I will checked the mass connection to the engine the wire did not look so good. It was connected straight on the engine and the connector to the engine was in not so good condition. I will improve this first.

Thanx for helping me out peanut. I appreciate it.

 

[peanut]

ok. Revving up by itself and slow for the revs to come back down to idle..... thats the classic sign of a lean or weak mixture usually caused by an air leak on the carb or the inlet manifold
if you removed your rubber inlet stubs when you cleaned the carbs then I would recommend you refit them applying some liquid gasket to both sides of the inlet rubber gasket . Threebond 1104 is the best but whatever you do don't use any kind of silicon gasket on the engine or gearbox.
Once the rubber inlet stubs are fitted with some threebond you can forget them being a source of an air leak between the rubber and the cylinder. The only time you'd need to remove the inlet rubbers again is if you were rebuilding the engine

Next check all over the carb for any tiny air leaks. Check around both the choke bodies and especially the joint between carbs and rubber inlets . Even a tiny tiny leak will cause erratic running and idle and an overheating engine.
best way to test for leaks on the inlet and carbs is to spray some carb cleaner or propane gas etc which will cause your idle to rise when it finds an air leak

you might find this helpful

 

[5twins]

If I'm reading this right, you have open pipes, "open" filters (pods I assume), and you haven't changed the jetting to compensate for those mods. Of course it's going to run lean. Eventually, you will probably burn a hole in one of your pistons too.

 

[peanut]

yes as 5twins says if you haven't upped your pilot jet by one size from 27.5 to 30 and your main jets by at least 2 then it will run lean. Shorty exhausts don't idle particularly well anyway .

5twins I thought it best to tackle one issue at a time rather than have the guy working on both ignition and fuel at the same time. Best to get a strong spark with a good battery first perhaps then tackle the carbs. We'll need to know which jets are fitted to advise further which will probably need the carbs removed again

 

[Ritchie]

Right. Thanx guys. I have new jets wich will suit the openairfilter and pipes. (checked with van de Heiden tuning)
I will fit these and take it from there. Got a new battery, still a weak spark.
You got to give me some time since I am abroad for the next couple of days.

I will get back to you guys next week. Thanks for helping me out guys !! Have a good weekend!

 

[Steve Brand]

Ritchie the 79 model is the best model in my opinion....... probably because I have a 79 too

Now we know that your bike is standard and unmodified that should help a lot with diagnosing the problem.

It sounds to me like you are going to need to go through the whole bike systematically checking and testing everything because it is clear it was not running properly even before you cleaned the carbs "Before I cleaned the carbs the engine was running a but rough"

If you have a good battery and the starter motor is working then that will turn the engine over quickly and should help you test-start the bike. If the battery is not holding a good charge then use a car battery with jump leads ,it will give your battery a big boost . You need a fully charged battery to generate a good strong spark.

Check your battery earth wire and clean the chassis connection. Make sure that you have a good strong spark to both cylinders before you mess with anything else.

The more things you fiddle with the more problems you can accidentally introduce . Just tackle one thing at a time. Fit some new spark plugs and remake the HT lead connections to the spark plug caps and coils .
Then you will need to check both your points gaps and test both the capacitors/condensors. Also check that the advance is moving freely and is not stuck
See if that improves your spark first.

Hi. Do you know if a "engine won't start" troubleshooting guide exists? Like a flow chart or similar?
I'm in a similar position. 1976 650c standard US model with points. Did run before renovating. Now not firing. So I'm doing what I think is the right thing....working on one aspect at a time.....checking/ replacing coils, condenser, plugs and points in an attempt to get strong spark. Rechecking the carburettors to make sure everything is standard and clean. I didn't touch the timing so hopeful that hasn't moved. But a comprehensive troubleshooting guide might be handy in case I've missed something. Don't know if such a thing exists?