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Makotosun

DT 400 Spark arrestor / silencer

  • Andy_C
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DT 400 Spark arrestor / silencer was created by Andy_C

Seen some schools of thought that say that the silencer / spark arestor is pretty restrictive and recommend removing the spark arrestor from the silencer by knocking it out, or drilling through it, others say no.

I am an inquisitive sort, so rather that wreck a perfectly good Krizman silencer / spark arrestor I have bought a cheap 2 stroke end can which I am going to try in place of the stock silencer / arrestor just to see what happens.

It will certainly be noisier as it is an absorption type end can, but has no internal restriction, it will be interesting to see if it makes the bike any livlier or just makes a lot of noise.

Obviousley keep a close eye on plug colour and engine temp.

Thoughts ?

The bike is running well, but the zero restriction end can might liven it up even more.
 
Ex Yam DT400C, Triumph Trident 660, Triumph 865, Kawasaki KH 400
24 May 2023 05:32 #1

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Replied by MarkT on topic DT 400 Spark arrestor / silencer

Two strokes need back pressure in the expansion chamber to make maximum power. Too much is not good for power. But not enough is bad too.
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
24 May 2023 05:55 #2

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Replied by RT325 on topic DT 400 Spark arrestor / silencer

Look forward to the results.
A good long well packed aftermarket muffler should still be reasonably quiet.
Have a RMX genuine alloy muffler on my 360 [when i use that pipe] It's a bit big & ugly but pretty mellow. It's deep though rather than long.
24 May 2023 06:43 #3

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Replied by Andy_C on topic DT 400 Spark arrestor / silencer

Mark - I get that, hence why this is just an experiment to satisfy my curiosity, and I shall be keeping a close eye on plug colour.

I shall report my findings....
Ex Yam DT400C, Triumph Trident 660, Triumph 865, Kawasaki KH 400
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Last edit: 24 May 2023 06:45 by Andy_C.
24 May 2023 06:44 #4

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Replied by Andy_C on topic DT 400 Spark arrestor / silencer

An update:
Alternate straight through end can fitted last night, does not seem to be any noisier.
It feels livlier than it did with the OE spart arrestor / silencer, and has not lost any of the bottom end.
Checking the plug, it looks to be running richer.
Going to refit the OE spark arrestor / silencer tonight and take it for another run, for two reasons.

1. To satisfy myself that it actually is livlier - can really only do it with the seat of my pants.
2. To see if the richness is associated with the silencer - guessing it is because the plug colour looked pretty good with the OE system fitted, if it is then I will re fit and drop the needle down a notch or two.

Will post further updates as / when.
Ex Yam DT400C, Triumph Trident 660, Triumph 865, Kawasaki KH 400
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31 May 2023 10:15 #5

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Replied by Andy_C on topic DT 400 Spark arrestor / silencer

Update:

Took it out yesterday evening following more or less the same route as I did on the previous ride with the free flowing end can.

Conclusion is that it runs better with the stock system, and the free flowing can does make it run richer.

Perhaps by fiddling with jetting I could make it run better with the free flowing end can, but for now I am content to leave as is, and just enjoy riding it.
Ex Yam DT400C, Triumph Trident 660, Triumph 865, Kawasaki KH 400
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31 May 2023 23:24 #6

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Replied by RT325 on topic DT 400 Spark arrestor / silencer

You'll be gettin bloody sick of my ideas but if it's "not louder" with the straight through one it has me thinking exhaust problems further in. Maybe yours is a 'very well wrapped' straight through one.
Also to run richer with the straight through muffler sounds odd.
I'll have to go back & read what i've missed along the way. Cheers & sorry to ruin ya night.
I've gotta learn how to use those emoticons & smileys haha.
31 May 2023 23:35 #7

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Replied by Andy_C on topic DT 400 Spark arrestor / silencer

No worries - I like messing around, it's part of the fun.

I was suprised how quiet it was with the non restrictive silencer, and more suprised it ran richer, I was expecting the opposite.

I did give the box the caustic soda treatment about 800 miles ago, not much came out apart from some oily sludge - perhaps it needs the barbecue treatment !

If anything it runs better with the stock setup, and yes, runs leaner.
Ex Yam DT400C, Triumph Trident 660, Triumph 865, Kawasaki KH 400
Last edit: 01 Jun 2023 06:34 by Andy_C.
01 Jun 2023 06:33 #8

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