10v v 12W engine

[skydemon]

Morning chaps, I want to get a new engine for my10v DT125LC to be bored out to 175 cc. I want to keep in the original engine standard and out the way. I’m getting old and I need the pension LOL. What are the differences? Is it the porting or gearing and are they compatible? As always thank you in advance for your wise words of wisdom 🙏🏼

[neil]

AFAIK the 10v and 12w are exactly the same the restriction on the 12w would be carb and exhaust, same as rd 10w and 12a. Neil.

[skydemon]

Thanks Neil

[simon998]

Ports are different on the DT. There's pictures on here somewhere of someone measuring the port heights.

The only way you'll get it to 175cc is with a re-sleeve or a 170cc bigbore kit. Myself, my dad and a few others on here all have 170cc+ 125lc's and theres a couple of good threads on here about what carb to use, clutch mods etc.

[simon998]

rdlccrazy.proboards.com/thread/57027/autisa-big-bore-175cc-piston

[neil]

Yes the barrel porting is different on the dt compared to rd. Ported for more low end. Also the gear set ratios are different apart from 5th. Neil

[museumman]

Mar 8, 2023 16:41:23 GMT 1 neil said:

AFAIK the 10v and 12w are exactly the same the restriction on the 12w would be carb and exhaust, same as rd 10w and 12a. Neil.

Has it ever been established that the 10W(10V) and 12A carb bodies were different?

The admin on the RD facebook club has been claiming for years that the "UK carb is FASTER" (strange terminology) like he does with the "uk barrels are faster" 🤷🏼‍♂️  So I would've thought this would apply to the DT. 
I've never believed a word said on there personally.  but Richard who restores the German bikes came to ask as he'd been pressured in person into believing it, he told me he's also had 11Y carbs.   Whenever I sold 10W carbs on ebay they went for twice, sometimes three times the price.

I've always been curious to see a drawing. These are not necessarily off the shelf carbs. Yamaha can spec them. I've noticed the tops, slides and cable reach differs from the stock shelf parts available today. I mostly deal with 1GU stuff now though. Yamaha boxed NOS VM26 carbs from Singapore were identical but not stamped 1GU. Mikuni's stock VM26 has quite a few differences. 

[simon998]

I've tried and measured both the 12a and 10w carb and I cant find any differences, both 24mm at the widest point. The 1GU measured 26mm and had the two pipes for the water to flow, well, the one I have does.

[museumman]

The 1GU measured 26mm and had the two pipes for the water to flow, well, the one I have does.

The 1986 1GU carb had the heater pipes (85 is without) I used to just cut the nozzles off and blank off the cylinder head as not riding in winter. 

I used to run 1GU VM26 carbs on 10W MK1s (VM24) when I suddenly started getting bad ones in (probably due to ethanol), and they seem to run exactly the same with perfect mixture despite having bigger main jet (same or nearly same size as 12A) I cant work out why both of these have bigger main jets, which is why I think some people jump to conclusions.

I've also run a 1GU carb on a TDR Belgarda (normally 28 Dellorto) which was still my fastest 125 at that point in time, so a quicker motor not being held back much by the smaller carb. Standard exhaust though.
1GU pipe is 0.8 slower on 1/4 mile than cheap Gianelli, 1 second slower than Turbo Kit pipe, standard jetting still looked ok. Need to do more experiments this year.

[skydemon]

Mar 10, 2023 14:10:17 GMT 1 simon998 said:

Ports are different on the DT. There's pictures on here somewhere of someone measuring the port heights.

The only way you'll get it to 175cc is with a re-sleeve or a 170cc bigbore kit. Myself, my dad and a few others on here all have 170cc+ 125lc's and theres a couple of good threads on here about what carb to use, clutch mods etc.

Thank you. I will check it out. I want to restore the original engine standard and then put the 170 in for my own fun. Hopefully it will beat or at least keep up with my bestys MTX 200 LOL