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Makotosun
Yet another DT400 project,the Super DT400.
- bluntz465
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Replied by Bigdog302 on topic Yet another DT400 project,the Super DT400.
I don't plan on it. BTW I think I found the reason for the ticking noise. the nut for the primary side drive pinion was backing off. the threads are weak in that area. it backed off to the point it locked the engine up! 
inside the engine otherwise was great. I did torque the nut but had the impression the threads were weak to begin with.
not sure if I will hunt for another engine to rob the crank out of or get this one rebuilt. I found a NOS crank half with what I need but it is not cheap! I found a whole 1975 DT400 engine for much less.
for now I got it back together but I am leery of that crankshaft. the torque spec was 50-65 ft lbs. I got it to hold at 40 Ft lbs of torque on the nut.
when the nut backed off and it stripped the threads on the crank as the nut butted up to the side cover a little at the end. I was majorly bummed out by this. pulling the head and inspecting the top end still looks beautiful and it is getting plenty of oil.
it got really noisy as it was idling then quit. glad I was not out riding it or anything,I was testing a silencer I put on it. need to weld a stinger back on the pipe to use the silencer.
for now I got the engine back together but have not run it yet. everything else in the engine is fine,main bearings,piston and cylinder still look great and it looks like it was burning nice and fat,plenty of oil and nothing at all burned up.
when the engine stuck I was freaking about it to say the least. the engine now since the nut was addressed turns over well and very smooth.
sorry I did not take pictures and I was a most unhappy man when I tore it down to look at it.
as far as temps when running,it did not get hot but it does run a little warm. of course it was hot and nasty humid as weather goes.
BTW,I did some more reading up on the MX400B. they confirmed my findings on power pretty much,lots of power and torque and it makes mucho torque at low rpm.
scroll down the page and you will find 2 MX400B tests there. the dyno tests confirmed what another test said in their dyno test. 38 HP at 8,000 rpm. for a engine that winds like this one does. it makes
excellent bottom end power. if you scroll up the page there is a 1976 YZ400C test and in the MX400B test,the MX400 actually made more power! the YZ only had 34 hp and the MX400B made 38. the test on the YZ400C actually blamed the silencer for the power loss and they mentioned piston life in a MX400B was pretty short. the tests in question is in the link.
I was scratching my head on the YZ400C test,awfully weak power,especially considering the YZ360 made around 39 hp but it was a lot harder to ride due to it's light switch power.
vintageyzinfo.tripod.com/
inside the engine otherwise was great. I did torque the nut but had the impression the threads were weak to begin with.not sure if I will hunt for another engine to rob the crank out of or get this one rebuilt. I found a NOS crank half with what I need but it is not cheap! I found a whole 1975 DT400 engine for much less.
for now I got it back together but I am leery of that crankshaft. the torque spec was 50-65 ft lbs. I got it to hold at 40 Ft lbs of torque on the nut.
when the nut backed off and it stripped the threads on the crank as the nut butted up to the side cover a little at the end. I was majorly bummed out by this. pulling the head and inspecting the top end still looks beautiful and it is getting plenty of oil.
it got really noisy as it was idling then quit. glad I was not out riding it or anything,I was testing a silencer I put on it. need to weld a stinger back on the pipe to use the silencer.
for now I got the engine back together but have not run it yet. everything else in the engine is fine,main bearings,piston and cylinder still look great and it looks like it was burning nice and fat,plenty of oil and nothing at all burned up.
when the engine stuck I was freaking about it to say the least. the engine now since the nut was addressed turns over well and very smooth.
sorry I did not take pictures and I was a most unhappy man when I tore it down to look at it.
as far as temps when running,it did not get hot but it does run a little warm. of course it was hot and nasty humid as weather goes.
BTW,I did some more reading up on the MX400B. they confirmed my findings on power pretty much,lots of power and torque and it makes mucho torque at low rpm.
scroll down the page and you will find 2 MX400B tests there. the dyno tests confirmed what another test said in their dyno test. 38 HP at 8,000 rpm. for a engine that winds like this one does. it makes
excellent bottom end power. if you scroll up the page there is a 1976 YZ400C test and in the MX400B test,the MX400 actually made more power! the YZ only had 34 hp and the MX400B made 38. the test on the YZ400C actually blamed the silencer for the power loss and they mentioned piston life in a MX400B was pretty short. the tests in question is in the link.
I was scratching my head on the YZ400C test,awfully weak power,especially considering the YZ360 made around 39 hp but it was a lot harder to ride due to it's light switch power.
vintageyzinfo.tripod.com/
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!
Dave
Jesus is Lord!
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Replied by Bigdog302 on topic Yet another DT400 project,the Super DT400.
I may need to do what you suggested to all the bulbs. it overpowers the indicator light bezels too. thanks for the suggestion! 
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!
Dave
Jesus is Lord!
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