Messages

211

Tech Talk / Re: replacing yamaha yz125x crank seals

« on: May 10, 2010, 09:29:38 pm »

Pretty sure you can Jim. However, why woundn't you split it and replace the main bearings and seals (I assume your changing them because of hardness due to age).

It would also be a quick check of the bearing cones inside the castings to make sure they aren't loose. And also just to make sure all the teeth are in the right place.

Sounds like your half way there anyway.

Peter B

212

Wanted / Re: 1985 RFVC xr250rf head

« on: April 16, 2010, 04:50:19 pm »

Hi All

You'll struggle to find a good head (unless this forum has one stashed away). The 200 and the 250 84/85 model had a run of soft valve springs. The valves ended up mincing the head, seats and piston. Years ago I rebuild one for a mates son. Luckily it would not start due to compression. Valve seats came out with valves when I pulled it down.

A good welder can fix most problems but look closely for cracks in the head around the valve seat inserts and between the seats and the plug hole.

Good Luck.
Peter B

213

Yamaha / Re: 1976 yz125x cdi problem need to troubleshoot

« on: April 13, 2010, 09:26:11 pm »

Hi Jim

Coil values from the three leads.

White / Red = 90
Red / Brown = 472
White / Brown = 560

Hope it helps

Peter B

214

Yamaha / Re: 1976 yz125x cdi problem need to troubleshoot

« on: April 12, 2010, 10:46:45 pm »

Hi Jim

I'll check my "X" coil ohm values tomorrow night. I had a similar problem when I got my bike. A quick check is to test the readings across the three wires from the stator. If I remember correctly I had one combination showed open circuit (no reading at all). One coil has two wires coming from it the other coil is in series with the first coil (joining wire from one coil to the other and then up to make third wire to CDI.)

Where's a piece of paper when you need it!!!!!

I'll get the readings for you.

Regards

Peter B

215

General Discussion / Re: Which VMX class is the best to Race in?

« on: March 28, 2010, 09:32:37 pm »

Hi 49

All of what Nathan said and a little more. Find a good pre 78 bike (and trail bikes are a great beginning) because any of those era's are great fun. Spend a season sorting it, riding it and getting to know others in your club. The wealth of knowledge in most clubs is huge. And, everyone has an idea on how to make your bike faster.

By the end of the season you will have a better idea of where you want to be riding the next year. Others in the club can help with leads to that sort of bike/class. You won't look back.

Personally, I like the classic 125 and the pre 70. I ride an AT1 Yamaha (trail bike) in the pre 70 and would never have a chance of winning against 250 and 360 unless there was that Steven Bradbury moment, but guys in that group all enjoy the spirit of the racing.

Good luck
Peter B

216

Yamaha / Re: New project

« on: March 07, 2010, 08:31:37 pm »

WMC

Save yourself the grief and just get an IT175 in fair condition. You could lower the suspension for the wife and have another set of forks and shock for racing in the 250 class (evo possibly).

That would be cheapest and simplest option. ( and with a little bit of work you could have it registered giving you cheap extra transport.

Regards
PB

217

Yamaha / Re: Need help identifying this Yamaha Monoshock!

« on: February 24, 2010, 11:06:19 pm »

I'm not sure if it came off a dirt bike. Last time I had my 125X shock serviced at Chivo's in Sydney he made the comment that these shocks were the same as the TZ750 around the same period. The differences he commented on was the size of the shock. (length? dia? not sure what he meant by that). That may also account for the thinner spring wire and two stage spring??

It's more than possible that you pick one of these up....

Regards
PB

218

Yamaha / Re: yammy ag bike

« on: February 16, 2010, 05:28:59 pm »

The simple test is if it has 4 head studs or 5.

The 4 stud model (pre 1980) is the older type bolt through for the barrel.
Their all good! Use to tow start an old holden with one when I stayed at a friends farm many many years ago.

PB

219

Tech Talk / Re: Yammie CT1 cdi

« on: February 16, 2010, 12:19:26 pm »

It does depend on if you want the lighting circuit.

I run a YZ125X system on my AT1 MX race bike. I made a different stator plate out of a 6 mm aluminum sheet. Took some work but is perfect and spins up fine. There's also a conversion using a DT175 system but again needs a bit of work.

http://www.vintagemxracer.com/at1mxproject.html shows a simple conversion with a bit of welding. I'm going to use this one on a street CT1 project I have in the future using the DT bits.

Good luck and let us know which system you end up with and how it goes.

PB

220

Tech Talk / Re: rust in bore

« on: January 28, 2010, 08:49:13 pm »

Metal

Save yourself some head aches later, put in a fuel filter ( the simple clear plastic triangle type so you can see fuel movement) . It might be a good idea not to wash your bike so often! If you do wash it then start it and ride it around the block to dry the inside and air filter out (plus what goes down the pipe!) One of the worst things a 2 stroke hates is to be left wet and unloved.

Good luck

Peter

221

Tech Talk / Re: rust in bore

« on: January 28, 2010, 04:45:01 pm »

Hi Metal

I'd take Doc suggestion, clean up the barrel, flush out the bottom end and re-assemble. There is a good chance the vibration is the bottom end but live with it. When it starts to sound like a bucket of bolts then do something.

In the meantime, same some money or ask on the forum for an old engine of the right vintage and build yourself a budget motor. The best part about that is you will learn heaps, there are various combinations of gear box sets and porting you could play with and we can all help. The rights parts can be found, bearings, rod kits and stuff for the right price you just have to know where to look. 

The end result may be one motor for commuting and one for playing with 

In many years you may achieve Yamie Grand Master status like Nathan S.

Peter

222

Tech Talk / Re: dt bottem end squeak/vibration

« on: January 15, 2010, 06:04:06 pm »

Metal

Check the engine mounts are tight for the vibration.
As for the squeal, it could be the little bearings at the transmission shaft.
Does the noise go away if your in gear and standing still or does it do it at all time (still and rolling).
Is the chain over tight?

Then we can progress to the next step!

PB

223

Yamaha / Re: yz400def top on 250 bottom

« on: November 30, 2009, 10:17:54 pm »

Hi Matt

The simplest thing is to find a DT400 D/E/F and just change the gear sets. Cases and crank are the same as the YZ400 D&E. 1M1 I think are the numbers your looking for. Everything else will do the job. Get Lozza to port it, fit a YZ piston and get set for the world of Big Bores.

Peter

224

Yamaha / Re: C/R DT1 gearbox

« on: November 17, 2009, 10:25:45 am »

I just picked up all the parts for a AT1 MX close ratio box from US. You can find the part numbers from the Yamaha site and do the search. I did have a quick look at the RT/DT stuff and they seem to have most if not all the gears. There are a couple of different ratios on some of the gears so you better pick the right ones.

The AT box cost about $140 US. plus postage and is ready a to be slipped in. Not sure what the RT/DT box would be worth in total but the ones I looked at seemed about the same price I paid.

Good Luck

Peter

225

For Sale / Re: MR 175

« on: October 21, 2009, 11:08:57 pm »

I seem to remember that the Honda said no to importing them so the Honda Dealer from Orange and one or two other dealers from across oz imported them as a group.

Now here's where the memory lets me down, I think the numbers were very low like 10 or 20 (250's) and maybe 50 (175's) or vise versa . A fellow apprentice picked up a new 175 from Orange (Bennett Honda I think) at the beginning of 1978 and was the last one on the floor. The story about the imports was in either T&T or ADB at the time and that had the actual numbers imported.

I also recall that the Canobalas Enduro in 1977 or 1978 had about 6 or 8 MR's in it and I'm not sure any finished!

The same year another apprentice got the XL 250 and there was light years between the two bikes. The MR was slow and low more like a DT175A in most ways apart from an added inch or two at each end, the XL, fast high and reliable.

PB