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Makotosun

1978 DT 400 timing

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1978 DT 400 timing was created by 78Dt400Kart

How do I check/ set the timing after the flywheel key sheers? I haven't been able to figure out how to do that; the manual just says line up the marks UNLESS THE FLYWHEEL KEY SHEARED.
Last edit: 21 Nov 2019 09:37 by 78Dt400Kart. Reason: clarity
20 Nov 2019 20:59 #1

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Replied by RT325 on topic 1978 DT 400 timing

Nothing to worry about regarding timing. Just replace the key & 'do it up Tight' this time & she'll be all good.
Just reading again what you say the manual says--all they''ll mean [confusingly] 'is' that if the key is sheared off then lining up the marks on the flywheel & stator will have no relation to where the piston is due to key gone. Don't worry--unless you've moved the stator plate on the three screws away from original marks the screws have made & if so then just fit the plate where you can see the screws have been--easy as.
I keep using this pic of mine to demonstrate how tight they need to be. Ok i get a bit brutal but it's a big thread & it's super important to be tight--as i'm sure you now realise although i don't know of course who fitted your one.
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Last edit: 21 Nov 2019 13:31 by RT325.
21 Nov 2019 13:10 #2

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Replied by MarkT on topic 1978 DT 400 timing

Not sure what manual you have... can't recall seeing one that mentioned "unless you have a sheared key".

1978 is CDI and as long as you haven't disturbed the stator plate, just replace the key and timing will be back to stock.

If you have removed or rotated the stator plate, there should be factory alignment marks on the stator plate and engine case... often really hard to see on that model... usually about at the 12 to 1 o'clock position.

If marks are not there, you need a dial indicator and can make a new one... not too hard... but marks should be there
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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21 Nov 2019 13:44 #3

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Replied by 78Dt400Kart on topic 1978 DT 400 timing

thanks a ton! I now understand the manual was saying that the flywheel and the case marks should line up unless the key sheared. I interpreted as they should be made to line up unless key sheared. I've got to hand it to these engines; They seem to be simple enough to not fail too often. I had my premix pump fail but not a problem i just adjusted my jetting for premix. But just seeing a 41 year old engine purr with only minor restoration gives me an odd sense of joy. I got mine& all the bits to make it run for $150 pretty stout engine for that price. Hope you guys don't mind its now powering a gokart but hey better someone use it than lose it right?
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21 Nov 2019 16:03 #4

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Replied by RT325 on topic 1978 DT 400 timing

Video of the Kart running would be great sometime. sounds like a 'weapon'.
21 Nov 2019 18:21 #5

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Replied by FrankC on topic 1978 DT 400 timing

Good thread. I save this to my favorites.
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21 Nov 2019 18:52 #6

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Replied by bluntz465 on topic 1978 DT 400 timing

You may want to lap the wheel to the shaft with some polish a bit when you replace the woodruff key maybe keep it from recurring.
1957 Cushman Eagle 1969 Honda 90 ATC 1969 Honda CB250
1973 Yamaha AT3 1974 Kawasaki KH440 1974 Honda XR75
1975 Suzuki TS75 1975 Kawasaki GreenStreak 90 1975 Suzuki GT550
1975 Suzuki TS250 1976 Suzuki GT550 1976 Indian Chief
1976 Yamaha YZ80 1978 Yamaha IT175 1980 Suzuki GS550
1982 Yamaha IT465J
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22 Nov 2019 17:50 #7

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Replied by Bobv07662 on topic 1978 DT 400 timing

When I checked the timing on my 78 DT400E it was about 1/16 of an inch past when the piston was in the right place. That indicates that it was "advanced". By the way the stator plate and engine case marks are aligned and have never been altered. (3000 mile bike) I remember having a similar timing discussion here once before with a member looking for info on a bike's overheating and detonation concerns.
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22 Nov 2019 18:00 #8

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Replied by RT325 on topic 1978 DT 400 timing

Not certain with the 400 but generally the cdi timing alters a little from the set mark even on 400's. Often find a long mark with a short mark either side & depending on revs it'll move within that range, so it's only realy on 'that' mark within a certain rev range. I know my suzuki mudbug 100cc bucket racer tweeked to rev to 14 grand [in theory with porting & pipe to match] altered heaps when i strobed it. The advance was way up there at low revs which it needed to try & get the best out of wild porting which robs the low end of any power it had, [if it had any in first place] but retarded of to about 16 degrees at high revs or even almost tdc at 14000 in that extreme motor [hand grenade but fast while it lasted]. Used to often throw RG400 pistons out the exhaust so started again with milder porting. I remember one 30 lap GP at the airforce base & [while leading luckily halfway through] the liner broke off below the inlet & locked it solid while passing between two other bikes when catching tail enders. Not sure who got the biggest fright but stayed on & skidded to a stop. One other mudbug motor [my boy this time] in another yearly GP at base & was going well then next thing the end broke off the crank & disappeared never to be found haha. We used to run without the mag cover to let as much heat out as possible but we still ran the full flywheel mag as couldn't afford an RM small rotor unit & the crank broke flush with the seal & took off into the fuel storage area as we used the streets within base back then plus a tarmac section. Fun days those & miss them heaps. Airforce guys had all the tricks & all the gear to do it with. The times have changed unfortunately & can't race out there anymore. Sorry--off subject--again.
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22 Nov 2019 19:12 #9

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Replied by 78Dt400Kart on topic 1978 DT 400 timing

I just put it up for the winter so i can't get any videos up for a while. But I did have a photo of the front end handy.

Last edit: 23 Nov 2019 11:10 by 78Dt400Kart.
23 Nov 2019 11:09 #10

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