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Makotosun

Timing question for '78 dt400

  • Blackwidow824
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Timing question for '78 dt400 was created by Blackwidow824

I'm still working on tuning this bike. Already repaired airleaks. Rebuilt the carb to try to eliminate a 5k rpm stutter. It had been running lean.
Here is is what my sparkplug looks like before and after the carb cleaning.

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Before

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After

Looks like I finally got it to run rich. Setting are 180 main, 80 pilot, needle clip on 2nd groove from top.
But it wants to idle high (2500rpm) despite the idle screw being all the way out. I probably need to recheck the float level again.

I pulled off the pipes to check TDC for timing and decarbonize them with a torch. And I pulled off the spark arrestor. What is this black sooty packing material? Do I need to do anything about it?

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And last. I found my timing mark! Needed a bright flashlight to see it; I was using the wrong mark. So here is my timing setting and dial indicator setting. The center mark on the magneto is about an inch from the timing mark. I checked this 3 times. Do I need to set the timing or is this close enough?

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Advice appreciated.
The following user(s) Liked this Post: Dave Schaub
Last edit: 23 Dec 2015 23:49 by Blackwidow824. Reason: Needed to add more history
23 Dec 2015 15:08 #1

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Replied by Blackwidow824 on topic Re:I need some experienced eyeball on this

This is a 78 Dt400

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23 Dec 2015 15:08 #2

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Replied by Bigdog302 on topic Timing question for '78 dt400

here is a pic of a 1978 DT175 stator,flywheel and engine cases. this setup is very similar to yours but timing on this 175 is set at 1.8 mm BTDC.

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this pic depicts the line on the cases and stator in alignment. when the flywheel is rotated backwards and then when the specified timing on the dial indicator is up,all 3 marks on the stator,flywheel and cases are lined up the timing is set.

also pay attention to the small hand on the indicator,it should read 2 and almost 3 and the large hand will be at 9 or 10 on the dial but not at 0.

you also need to "zero" your dial indicator too before attempting to read the timing. bring the engine up on top dead center and with the small hand at 5 mm and the large hand on 0, rotate the engine backwards to 2.9 mm is read on the dial indicator and check all 3 marks. they should be all aligned then.
2 1968 DT1s,1970 RT1M,1970 DT1C,1971 RT1B,1971 Honda Z50K2,1974 DT100A 1974DT250A,1974 Honda MT250,2 1975 DT400Bs,1975 Honda CR250M1,1978 DT175E,1979 Honda CR250R.
Dave
Jesus is Lord!
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Last edit: 24 Dec 2015 16:38 by Bigdog302.
24 Dec 2015 16:30 #3

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Replied by Bigdog302 on topic Timing question for '78 dt400

this is a video of myself checking the ignition timing on a 1968 DT1. timing spec for these is 3.2 mm BTDC. since it has points I am using a buzz box.

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the buzz box makes a noise until the points close. you want your timing in this case to the make or break point at 3.2 mm BTDC. when you get to that point the points just start to open again right at 3.2. when the points break open this triggers the spark and you set it via the point gap setting.

for quick and dirty settings in the field, I store the point gap I recorded when I set the timing and use a feeler gauge to determine the exact point gap for easy reference when a buzz box and dial indicator is not there with you.
2 1968 DT1s,1970 RT1M,1970 DT1C,1971 RT1B,1971 Honda Z50K2,1974 DT100A 1974DT250A,1974 Honda MT250,2 1975 DT400Bs,1975 Honda CR250M1,1978 DT175E,1979 Honda CR250R.
Dave
Jesus is Lord!
Last edit: 24 Dec 2015 16:46 by Bigdog302.
24 Dec 2015 16:45 #4

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Replied by Blackwidow824 on topic Re:Timing question for '78 dt400

Mine has a CDI so I'm not real clear how to adjust. The manual says to remove the magneto cover and loosen to base plate to line up the marks. Not much explanation. And I need to buy a tool to remove the cover. But there are 3 marks on the magneto cover. Why?

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24 Dec 2015 19:46 #5

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Replied by Blackwidow824 on topic Re:RE: Timing question for '78 dt400

That's a great explanation! Thank you so much. I wasnt sure what to look for to confirm correct settings. This will help a lot.

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24 Dec 2015 20:11 #6

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Replied by Blackwidow824 on topic Re:Timing question for '78 dt400

And Merry Christmas Bigdog! I appreciate you taking the time to post.

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24 Dec 2015 20:13 #7

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Replied by Bigdog302 on topic Re:Timing question for '78 dt400

I hope it is enough to get you through. Merry Christmas Black Widow! :Buds
2 1968 DT1s,1970 RT1M,1970 DT1C,1971 RT1B,1971 Honda Z50K2,1974 DT100A 1974DT250A,1974 Honda MT250,2 1975 DT400Bs,1975 Honda CR250M1,1978 DT175E,1979 Honda CR250R.
Dave
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25 Dec 2015 00:07 #8

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Replied by Bigdog302 on topic Re:Timing question for '78 dt400


if it were me, I would remove the flywheel then align the mark on the stator with the mark on the case.

you can use the dial indicator once the flywheel is back on to verify the setting.
2 1968 DT1s,1970 RT1M,1970 DT1C,1971 RT1B,1971 Honda Z50K2,1974 DT100A 1974DT250A,1974 Honda MT250,2 1975 DT400Bs,1975 Honda CR250M1,1978 DT175E,1979 Honda CR250R.
Dave
Jesus is Lord!
25 Dec 2015 00:21 #9

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Replied by FrankC on topic Re:Timing question for '78 dt400

I will need to time my 78 as well in the future. I hope you don't mind 824 if I ask what the scribed mark on the case itself represents. Is it tdc, or a mark to indicate timing btdc. If a new piston, rod assembly is installed, do these marks still hold valid? Thanks.
25 Dec 2015 13:44 #10

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