Author Topic: Barrel Mods  (Read 1265 times)

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Offline R1slider

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Barrel Mods
« on: January 14, 2018, 07:12:39 AM »
Hi All,

I have a question relating to modding the cylinder...

The god who is Stan Stevens (Legendary Two Stroke Tuner) says you can modify the spigots at the bottom of the cylinder. This would be where you have removed the carb and reeds, and as you look in towards the crank you can clearly see the cylinder sleeve obstructing the inlet charge flow.

As I have just paid £250 to have the worn cylinder re-sleeved, I am a bit concerned about wrecking my newly refurbed cylinder.

Has anyone done this mod? - main risk I can see is accelerated wear as the Piston will be more free at the bottom of the stroke..

Offline alex_d

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Re: Barrel Mods
« Reply #1 on: February 03, 2018, 08:37:19 PM »
Well, this coming back and back again ... that DT engine / cylinder is an old skool design - developed from Minarelli 125cc.
you can tune it and tune it but it will never match modern 2T.
MC Motorcycle suicidal tendencies ;D

Online 4V5

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Re: Barrel Mods
« Reply #2 on: February 03, 2018, 11:23:44 PM »
Well, this coming back and back again ... that DT engine / cylinder is an old skool design - developed from Minarelli 125cc.
you can tune it and tune it but it will never match modern 2T.

yeah Alex.. but this is a yamaha forum with a DT board... so whatever limitations the DT engine may or may not have.. that's what we are dealing with.. what the DT engine lacks in modern performance it more than makes up with by being bulletproof.. the only issues seem to be when people f__k with them that shouldn't f__k with them.

As I have just paid £250 to have the worn cylinder re-sleeved, I am a bit concerned about wrecking my newly refurbed cylinder.


I'd pay the money and send it to Stan Stevens, or any reputable tuner if you're concerned about longevity. I'll add there are other places that can be modified in the barrel to achieve exactly what you are chasing if you're clear with the tuner what you're after you'll get it.

I've got a pair of Stan Sevens RD250LC barrels and they are bonkers.. if the mod you are thinking of is what's been done to these... yeah lol... would I want that type of power delivery on a trail bike at the bottom of a gully... umm no.

having said that.. I read up on what mods worked, I listened to old timer's when they said their old school tricks and applied them myself... in the backyard with some rats tails files a rotary burr and a decent clue as to where to modify it.

I have done a couple of DT175 engines that are impressive.. longevity hasn't been an issue and they go better than any DT has a right to go.




the main thing to ask is... what is the DT going to be used for?
IT465x4 IT400C IT175Fx2 IT175G YZ465G YZ250C YZ250WR RD350LC RD250LCx5 DT175Nx2 TW200x2 DT200L DT200R RT3 GT80F YZ80L PW50J KH250B1 PE175C TS250ER TS185ER KX60 KTM50 AG175B AG100

Online poirson

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Re: Barrel Mods
« Reply #3 on: February 05, 2018, 05:41:36 PM »
Hello everybody !
One easy thing you can do is to review the squich value. Normaly, it is about 2,00mm and it should be near from 1,2mm . It makes a big difference when you are riding your bike... my bottom-end is like a new one but now my the clutch is not strong enough..
You just have to run with 98 Octane benzene.
Try it, you will tell us news 8)

Offline alex_d

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Re: Barrel Mods
« Reply #4 on: February 06, 2018, 06:05:58 AM »
right ... with this comments: go ahead and tune the sh_t out of that DT,

please let us know next;
 - the time spent for the whole project,
 - the efficient time of riding this bike trouble free,
 - how expensive was the project

MC Motorcycle suicidal tendencies ;D

Offline R1slider

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Re: Barrel Mods
« Reply #5 on: February 06, 2018, 06:52:35 AM »
Lol - I know alott about 2t tuning, just never done the mods I was asking about :  ) when I eventually get around to it, i will post a pic with the issue - it will affect every 200R on this forum.


Online 4V5

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Re: Barrel Mods
« Reply #6 on: February 06, 2018, 08:57:41 AM »
right ... with this comments: go ahead and tune the sh_t out of that DT,

please let us know next;
 - the time spent for the whole project,
 - the efficient time of riding this bike trouble free,
 - how expensive was the project

didn't you blow yours up?

I'll start with mine aye.. it's a 175 but.. meh.. same things I did to mine work with the 200

an afternoon. in the backyard.. with a rotary burr and a ratstail file for the barrel
a sheet of glass and some sand paper for the head.
a set of reeds and a muffler.

$200 all up.. including refreshments.

a full year of road duties (about 10,000km) plus 5 laps of cookardinia vinduro without laying a spanner on it except for the coil breaking off the frame.

stock with me on it 90km/h.. after my mods.. 120km/h.. all day every day..



http://www.vinduro.com.au/3638/yamaha-dt175-1985/



Hello everybody !
One easy thing you can do is to review the squich value. Normaly, it is about 2,00mm and it should be near from 1,2mm . It makes a big difference when you are riding your bike... my bottom-end is like a new one but now my the clutch is not strong enough..
You just have to run with 98 Octane benzene.
Try it, you will tell us news 8)

definitely.

one of the overlooked things is less is more.. a simple thing to do is to have a look at a DT barrel.. and look at an IT barrel then a YZ barrel.. mid 70's > you can see what differences that have been done to the barrels at the factory have done to change the performance.. the exhaust port is the thing everyone sees. transfer ports are another.. the 5th port above the inlet is another,

have fun!!
IT465x4 IT400C IT175Fx2 IT175G YZ465G YZ250C YZ250WR RD350LC RD250LCx5 DT175Nx2 TW200x2 DT200L DT200R RT3 GT80F YZ80L PW50J KH250B1 PE175C TS250ER TS185ER KX60 KTM50 AG175B AG100

Online mikeyvet

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Re: Barrel Mods
« Reply #7 on: February 06, 2018, 11:43:56 AM »
I reckon they go pretty good standard.

Having said that I just put on a set of boyesen reeds and a free flow muffler and the bike is plenty quick enough for me on a dirt trail, and it would only take an hour to return to standard.

Online poirson

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Re: Barrel Mods
« Reply #8 on: February 06, 2018, 05:27:21 PM »
Hi !
No trouble if you reduce the head with a milling operation: Yamaha says that 5/10 is a correct value.
My bike is running every days in summer, on and off road. At this moment, the engine is running with 7/100, clearance between cylinder and piston (Prox), it is to much  ::) so I will test a Wossner piston with 55µ. My bike will be a like bomb ! (Taper is not so important than Prox.
Two years ago, I tested a YFS Vertex piston, it was very powerfull but I had a little trouble (because of me..) the clearance was 45µ.
For the diagram: never make any modification to the exhaust port: timing is very high : 200° but transfer ports are down .. 122°
now, lateral transfert ports are about 126/127°
another important point: reeds : Boyesen are not working on my bike. the best results I had is with Bihr carbon fibers one. I will send you photos about my bottom-end...
My bike is very reliable .

Offline alex_d

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Re: Barrel Mods
« Reply #9 on: February 06, 2018, 07:21:16 PM »
Hi !
No trouble if you reduce the head with a milling operation: Yamaha says that 5/10 is a correct value.
My bike is running every days in summer, on and off road. At this moment, the engine is running with 7/100, clearance between cylinder and piston (Prox), it is to much  ::) so I will test a Wossner piston with 55µ. My bike will be a like bomb ! (Taper is not so important than Prox.
Two years ago, I tested a YFS Vertex piston, it was very powerfull but I had a little trouble (because of me..) the clearance was 45µ.
For the diagram: never make any modification to the exhaust port: timing is very high : 200° but transfer ports are down .. 122°
now, lateral transfert ports are about 126/127°
another important point: reeds : Boyesen are not working on my bike. the best results I had is with Bihr carbon fibers one. I will send you photos about my bottom-end...
My bike is very reliable .

Poirson, can you explain next (measurements?);
 -  5/10
 - 7/100
 - 45µ
 -
MC Motorcycle suicidal tendencies ;D