| Author |
Message |
Robert
| | Posted on Sunday, May 21, 2006 - 5:52 am: | |
I've been trying off and on to get my T20 to run for almost a year now. I've cleaned the carbs and I have spark but it just won't run (I did have it running fine last year). I noticed some arcing across the points when I kicked it over so I installed new points and condensers. I checked the coils and measured 4 ohms across the primary and 8600 ohms across the secondary for both coils (I assume within range). When I set the timing I came across a strange thing, with the points open I read 8 ohms resistance for each point. If I disconnect either one of the condensers I get no continuity with the points open (as you would expect). The other way I can break the continuity with the points open is to disconnect any of the leads off the coils (orange, black or white). I'm guessing that I have a short but I have no idea where it is. Even with this short I still get spark with the plugs laying on the side of the head but it does not appear to be strong enough for the engine to catch. Anybody have a similar experience? |
Adrian
| | Posted on Wednesday, May 24, 2006 - 6:53 pm: | |
Hi there
If you have a spark, you can't be far wrong. Is your battery fully charged by the way as this will make the spark stronger?
If you have a spark, it should run. Are you sure fuel is getting through? If you push it up and down the road with the throttle open, are the plugs soaking afterwards?
You also mention that you've been looking at it on and off for a year. Have you got fresh fuel in? As fuel sits in the tank, the volatile compounds evaporate leaving behind a mixture that is hard to burn in an engine. Dump your old fuel and try new.
Let me know what happens..
Adrian |
Robert
| | Posted on Monday, May 29, 2006 - 11:30 pm: | |
I just bought a new battery today. I've been using the battery from my other bike, which has a magneto system and doesn't need a fully charged battery to run. I'll try the new battery and fresh gas and let you know how it turned out.
Thanks,
Robert |
Robert
| | Posted on Thursday, June 15, 2006 - 6:07 pm: | |
Hi Adrian,
I bought a brand new battery (measured 12.2 volts) and filled up the carbs with fresh fuel. When the bike runs it almost always starts on the second kick. This time around it caught on the second kick and ran for a split second then died. With repeated kicks wouldn't catch again. I pulled the plugs and they were both wet. I still think that I'm not getting a full spark. The spark that I do get is thin and purple/blue, although at times it appears as slightly yellow. I presume that it should be a nice fat blue spark that makes a sharp cracking sound when you kick over the bike. I'm running out of ideas as to what to try next.
Robert |
Adrian
| | Posted on Thursday, June 15, 2006 - 7:38 pm: | |
The golden rule with problems like this is to realise that if an engine has THREE things, it HAS to run. The three are:
- Fuel in the right ratio
- Compression
- A spark at the right time
The other 'golden rule' is to make no assumptions about which factor is the problem!
Lets concentrate on the spark for now. Your spark does seem OK from your description but this may not be the case under load. One possibility is that the condensors (capacitors) by the points are faulty. This would affect the running and may be the problem. It is the easiest, and cheapest item to replace as many std car parts can be made to fit temporarily if you don't have any spares.
The other candidate is the HT coils which may be breaking down under compression. I had this on my race bike recently where it would only run on one side despite two decent sparks. Again, if you don't have any decent spares, some other bike coils can be tried out to see if that helps.
Incidentally, have you tried to bump start the bike? I'd be interested to know what happens when you push it along for 10-20 yards in first gear.
Does this help? |
Robert
| | Posted on Friday, June 16, 2006 - 12:40 am: | |
You brought up some good points, some of which I already thought about. I've thoroughly cleaned the carbs and replaced the usual stuff with a rebuild kit. The last time I checked the compression it was 155 on the left and 160 on the right (throttle closed). I have already replaced the condensors with ones I bought from Paul Miller but they did look like they've been sitting awhile on the shelf and kicked around over the years (I'll take them off and check them). I've long suspected the HT coils but the resistance readings across the primary and secondary looked ok (I'll still try to hunt a good pair down). I'll also try to bump start and see what happens. |
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