dt 175 mx

[mxrider]

Hello all ,,,,,could any put im the right picture?????,ihave a dt mx ,i have raised the top of the exaust port ...all is ok, a bit more mid boost..i have a gianeli exhaust ,trying to get a bit more pwer out of the engine,,,i have been told i could advance the timing !!!!!!COULD THIS BE A GOOD OR BAD IDEA ??,does any one have any more sugestions that are proven on there dt.....thanks for reading ,,

regards mx rider

[Airhead]

Have you seen This post?

You need to increase the main jet size, what size have you got fitted?

You could also try a set of Boyesen reeds

[mxrider]

Have you seen This post?

You need to increase the main jet size, what size have you got fitted?

You could also try a set of Boyesen reeds

hello thanks for the reply,i did look at the link.mm thats a lot of work,,,i will look at the jet,not to sure of size would that make a big change?? im thinking of having the barrel stan stephens ..tuned ??

[mxrider]

hello thanks for the reply,i did look at the link.mm thats a lot of work,,,i will look at the jet,not to sure of size would that make a big change?? im thinking of having the barrel stan stephens ..tuned ??

o.. and any idea on timing!! i thought it might pre detonate???but was told it will give a bigger power band??

[Airhead]

hello thanks for the reply,i did look at the link.mm thats a lot of work,,,i will look at the jet,not to sure of size would that make a big change?? im thinking of having the barrel stan stephens ..tuned ??

You need to put a bigger jet in with that Gianelli pipe fitted, its less restrictive than the original one, standard jet is a 130, you would be wise to buy the next two sizes up, i think thats a 135 and a 140.

I would put the 140 in first and plug chop it.

You would be wise to get Stan Stevens to do the work rather than do it yourself, if you do...let me know how it goes, i considered doing it myself but havent got around to it.

[mxrider]

You need to put a bigger jet in with that Gianelli pipe fitted, its less restrictive than the original one, standard jet is a 130, you would be wise to buy the next two sizes up, i think thats a 135 and a 140.

I would put the 140 in first and plug chop it.

You would be wise to get Stan Stevens to do the work rather than do it yourself, if you do...let me know how it goes, i considered doing it myself but havent got around to it.

ok i will let you know ,I call his work shop from the no ,on his web site ,www.stan stephens .co.uk.i was quoted £140,that would inclued the head and they would do the sqwish band!!! and you can have it ported to any style i:e low mid or high range.

anyway i will keep yiu informed

[Airhead]

BTW Your post is for a 175MX and your bikes owned is a 125MX

[racerd]

ihave a dt mx ,i have raised the top of the exaust port ...all is ok, a bit more mid boost..i have a gianeli exhaust ,trying to get a bit more pwer out of the engine,,,i have been told i could advance the timing

when you raised the exhaust port did you chamfer the edge this is to help the piston rings go over the port if you did not chamfer the edge of the port this could break the piston rings and wear them out faster,

if you want more power then try looking at bigger carb, open out the reed stops, change reeds, port and flow reed block

set the squish up to just under 1.0 mm, port the inlet port, match up transfer entrances to crank cases,

if you advance the timing too much this causes detonation holed pistons and makes the engine run slower, also when tuning you need to do a plug chop to see how the mixture is burning in the cylinder if you run lean then you get power fade then a nip up and or seize up and holed pistons,

you could try using a racing spark plug and plug cap

[Cynic]

Have you seen This post?

If you re-read that post and clear out the waffle he has used an IT175 barrel/piston etc with an it carb and a cobbled exhaust. No mention of ANY work on the crank/mains etc. Wouldnt mind betting an IT chimes in at around there HP wise. 80mph in 4th, on 22hp. A Dt125x with the full power ypvs gubbins has 22hp and thats flat out at less than that.

As the username suggests i'm afraid i need proof.

Back to it.... Unless you have got some serious tuning going on its not really worth it. As you need to mess about richening the mixture for when its on the pipe which makes it way too rich lower down. Been there done it with the 50.

Editted out as its total Boll....(The ig timing on the 175 is set in stone, you will be machining the stator plate to get any adjustment, then you will be advancing the entire ig curve.)sorry.

[racerd]

QUOTE (yamafun @ Dec 30 2006, 08:26 AM) *

MY 1979 YAMAHA DT175 HAS 22 HORSEPOWER AT 12000 RPM. MAX RPM IS 13000RPM. DYNO TESTED USING A DYNOJET 2 WHEEL AUTOMOTIVE DYNO. USED ONLY ONE ROLLER INSTEAD OF BOTH. ORIGINAL HORSEPOWER WAS APPROX 14 HP AT THE WHEEL AT 7000 RPM. MODIFICATIONS ARE THE FOLLOWING:

IT175 CYLINDERHEAD MODIFIED ON A LATHE; SHAVED CYLINDERHEAD BUT MADE COMBUSTION CHAMBER WIDER. OCTANE USED 91 OCTANE. USED 1977 IT175 CARBURATOR MODIFIED; BORED OUT TO REDUCE VENTURIS. REJETTED ON THE STREET FOR THROTTLE MAX AND FULL THROTTLE; MAIN AND IDLE JETS. K&N AIR FILTER. STOCK CYLINDERHEAD BORED TO FIRST OVER, PORTED TO SPECS OF 1977 IT175 PORTS SIZE. EXPANSION CHAMBER FROM 1991 HONDA CR125 MODIFIED TO FIT. MUFFLER PROCIRCUIT FROM 1991 HONDA CR125 MODIFIED TO FIT. 4TH GEAR WILL HIT APROX 80 MPH. HAVE NOT TRIED 5TH AND 6TH GEAR. BIKE IS TOO LIGHT FOR THOSE HIGHER SPEEDS. DO NOT TRUST BRAKES FOR THOSE SPEEDS. NEED TO UPGRADE FRONT DRUMS TO DUAL PISTON DISC BRAKES.

12000 RPM. MAX RPM IS 13000RPM. this is for the race track on the road 11,000/11,500 spot on,

STOCK CYLINDERHEAD BORED TO FIRST OVER = IT175 CYLINDERHEAD MODIFIED ON A LATHE. at what angle was the squish re cut to and did you measure the squish also this lines up the edge to the cylinder bore,

CARBURATOR MODIFIED; BORED OUT TO REDUCE VENTURIS. what size is the carb now,

REJETTED ON THE STREET FOR THROTTLE MAX AND FULL THROTTLE; are both the same meaning,

wot = wide open throttle,

K&N AIR FILTER. have you oiled the filter

also you need the reed block porting and flowing and finishing off in 80 grit production hone marks this aids the mixing of the fuel and oil into the engine

taper port the front of the carb

open out reed stops

inlet port open 360 degree reed block stops and starts flow

exhaust port 22mm from top of cylinder liner and make the exhaust port wider as well

guide inlet flow towards boost port

line up transfer entrances on the barrel to crank cases

the ports need a 2mm chamfer at a 10 /12 degree angle

flat and polish piston crown and combustion chamber in cylinder head and the exhaust port

bigger carb

if not using a boost bottle then connect one

set squish to 1.00mm