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Discussion Starter · #1 ·
I recently replaced my Sparx rec/reg as it blew up (figuratively), new carbs and new fuel lines. I put a Boyer rec/reg in, 6 volt coils and reset the valves since I had the tank and carbs off any how. The bike rode great for a couple hours, then started backfiring a out of the exhaust. Then an hour later or so I noticed it was also backfiring into the left carb a little. Finally it stalled out. It was hard to start again and would stall if the revs got below 4k or so. I checked the rec/reg after letting the bike sit over night, 14.5 volts at the battery till about 3,000 rpms. After that there was a voltage draw. Any ideas whats up? I was thinking I gapped my valves wrong (feeler gauges are still a bit of a mystery to me) but not sure what else it could be.
 

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What is a voltage draw?
Voltage decreases?
If you are sure the ignition timing is OK, try a couple of new plugs.

As for gapping the tappets, it`s awkward with the round rocker caps.
People make their own feelers I think, a .002 (in) and .004 (ex) mounted on a thin bar at right-angles
When you do it,ensure the rocker arm is lifted or it will seem to be a good sliding fit anyway.
And doulble check after tightening the nuts.

How old is the fuel?
Undo the carb drain screws under the bowls and check for water.
Do a fuel flow check, and make sure the tank-cap breather hole is clear.
 

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Discussion Starter · #3 ·
Thank you for the reply. I have a Boyer and even with my Boyer fully advanced, when strobe timing the bike, it is firing just ever so slightly retarded... so the timing is not perfect.

I'm not sure what you mean about making sure the rocker ARM is lifted or it will seem to be a good sliding fit? If the rocker wasn't lifted would there be any gap? How do I know that it is lifted besides there Bing a gap?

The fuel is new, or was at the time only pumped at the station a few hours before driving. When I was riding one of the bolts holding my center stand fell off (I don't know how either but this is the second time) so tomorrow my new mounting set for the center stand should arrive and I will put it in. Then I will readjust my valves and drain the bowls. I was thinking of using my TDC tool to located TDC and then just setting the compression stroked side, both intake and exhaust, at the same time. Then dong the other side. My shop manual says to just find where the left exhaust valve is depressed maximaly and sets the other sides exhaust, and then repeat that process for each valve but I think my way would.be.more accurate, what do you think?
 

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I think you should follow the shop manual. I have been doing that for years with success.
Put the bike on it's centerstand and put it in fourth gear with the plugs removed and rotate the back wheel to move the pistons. It's easier that way.

I bought a set of tappet adjusters that take an allen key instead of a wrench. It's easier to hold the tappet adjuster in place while you tighten the nut. So it's more accurate.

When you get your bike running correct the ignition timing asap.

Did you check for a nice fat blue spark from your plugs yet?
 

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Discussion Starter · #5 ·
Ok thanks Danpos. The reason I was thinking of using the TDC tool is because if your setting the intake for example to .002" that is such a tiny little gap. If the left intake say looks like it's fully depressed but what if its not quite, like a tiny little bit before or after maximum depression wouldn't that effect the valve gap?
I will check for a good spark as I haven't yet.
Lastly, as far as correcting the timing. My Boyer is fully advanced, I considered filing down the slots where the mounting screws go so that I could advance a little more because the strobe timing is showing me that it is still a little retarded. What do you think about that?
 

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Using the method I described while holding your finger on the valve is easily accurate enough. You can detect even the slightest movement. Try it and you will see.
Trust me when I say that even the slightest flinch while tightening the nuts will knock your valve clearance off far more than the method I described.

The .002 feeler gauge isn't an issue. I have a 1971 with the small round covers.

DON'T file the boyer plate! It sounds like you didn't assemble it right. Move the plate with magnets a little instead.

Before you try to start your bike make certain that everything is setup right.
It would be a very sad thing to do any mechanical damage do to a poor tune up.
 

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If you get that other valve anywhere between 1/2-open and fully open,you'll be fine.It's still better than using TDC.
I don't trust using feeler gauges on worn (indented) valve tips.A dial gauge works well.Just backing off 1/16-turn (intake),1/8-turn (exhaust) works OK.
 

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"I'm not sure what you mean about making sure the rocker ARM is lifted or it will seem to be a good sliding fit? If the rocker wasn't lifted would there be any gap? How do I know that it is lifted besides there Bing a gap?"

What I meant was, when you have a gap and the feeler seems good, push the arm up,to ensure the gap is not larger than it is.:)
 

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Discussion Starter · #9 ·
Thanks Danpos. The play with the two magnets has two slots for the two screws that mount it. I cannot turn it any more because the screws are at the end of the slots. I will take a picture of it. Thanks! O have not and will not file it.:)
 

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Discussion Starter · #10 ·
thanks Mr. Pete

Thanks for clearing that up Caulky. I'm not that smart so I sometimes need things spelled out for me, heh.
 

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Thanks Danpos. The play with the two magnets has two slots for the two screws that mount it. I cannot turn it any more because the screws are at the end of the slots. I will take a picture of it. Thanks! O have not and will not file it.:)
I know exactly what you meant.
Under that plate is the plate with the magnets on it. Remove the plate that you rotate and remove the plate with the magnets on it too (magnetic rotor). Making note of where it was. Move it slightly in the direction that you ran out of travel then you can set the timing correctly.
 

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Discussion Starter · #15 ·
Alright, so now that the tim8ng is cleared up the bike still runs horribly. I can twist the throttle 3/4 open and no response, it just keeps the bike from stumbling to a stall out. Then, wide open the bike will rev up and accelerate rapidly, then cut back suddenly, then stumble and almost stall, then rev up and accelerate rapidly, then stumble and almost stall, etc...What do you think? Rec/reg is good, battery is good, timing is good, gas is good.
 

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What colour are the plugs?
Sounds as if its very rich!
Poor sparks because of soot, which burns off occasionally? :confused:
 

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Just a thought - Have you checked to be sure your main jets have not unscrewed some?

Mark
 

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Discussion Starter · #18 ·
It is definitely a little rich but not too bad.

Yes, thank you I forgot to mention that I checked the main jet and it is secure. Also, the needle is secure and moves up & down with the slide.
 

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Could the screens in the gas tank petcocks be plugged? Suspicious that it sat for a while, while you worked on it, then these problems started. Junk could have settled down to the bottom of the tank.

If you have a voltmeter with DC and AC scales, switch it to AC and put it across the battery while it's running. If you see more than millivolts, the rectifier pack is either hooked up wrong or faulty. It will do bad things to the ignition controller.
 

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Discussion Starter · #20 ·
Thanks, I'll test the battery when I get home from work tonight. I believe the petcock are adequately clean because I put brand new clear tri-cor fuel lines in and I can see a nice steady flow of gas.
 
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