Well hard to believe it has been a year already since I put the first details down on paper to create a vintage Yamaha Enduro trail rider!

This bike has since become known as my "Black Widow"

This image is hidden for guests.
Please log in or register to see it.

This image is hidden for guests.
Please log in or register to see it.

So thought it would be good to give an update on how things have progressed since then and where the bike has been put to the test.

As you can read in the thread... This was not an easy project to simply put many parts and components together from different years, specs etc and have everything work perfectly day one.

This has truly been a labor of love and has taken almost 12 months to finally get this bike tested and dialed in with one final step to go.

When I debut this bike last August in Ouray, Colorado- it only had 500 miles on the freshly bored Cylinder and was not put to any test prior to showing up for EnduroFest 2014- so it was a real shot in the dark to see how she would perform...

It ran/worked at about 70% due to many factors, but the bike made it thru many rides even the "Trail for Hell" so it ran good enough to get through some amazing rides but I knew it was going to require a lot more work to get this bike performing at a very high level.

So with many things to check and recheck, replace, test ect. thru the winter- the bike has come a long way.

Its last trip out to California in March- we found that bike was having some pinging issues and with the help of my good So. Cal Friends (Dave Meis and DVM) we re-jetted and retarded the timing a tad to get the bike calmed down and even though there was some power loss with the retarded timing, it really started to feel like I was just about to zero in on this bike. Plenty of power to run 60 mph down the road and get the front end up thru 1st and 2nd gear on the trail-Love That!!

So when I got home- Put the compression tester on it and it hit a whopping 160 PSI with the High Compression head!! No wonder there was some pinging!

The bike had test very consistently at 150 PSI before I left for the trip to Cali and did not want to exceed that any further for sure... but during the trip to Cali and home it changed and could of created some real issues with long term use.

So- I reset the timing back to stock and pulled the MX Head a couple of days ago- Put the stock head on and she is sitting at 125 psi now.. Bike runs really good!

So that final step that I spoke about earlier is to get the "Stock" head milled down a tad to get that compression up- to settle in at 140 to 145 should give it that little extra pop that I had with the high compression head but keeping the compression level in check.

With this final step- the bike should be at 100% and will deliver many more miles of fun and power.

Will update once I get the head back from my Machine Shop and give it a try.

I got to see this bike and ride with Greg in California a few weeks back - the pictures of the bike really do not do it justice. It is nicer than a lot of museum bikes I have seen, but it is not a garage queen! It really goes and Greg doesn't baby it.

I love the fact that it is not sitting in a dusty garage and is instead being enjoyed!

I have used 100LL aviation fuel on first pass cleaning on any parts. Works fantastic and whatever is left over it quickly evaporates. If u don't mind using a benzine based product. I normally wear gloves and keep away from open flames or sparks.

Time to give my 1971 Yamaha "Black Widow" RT1 a complete redo/rebuild!

This image is hidden for guests.
Please log in or register to see it.

I have now put over 4,000 well ridden miles on this bike which has attended every riding event we have had over the past 4 years... from California Dream'in to Ouray Colorado twice- Eureka Springs- Moab- Beaver UT etc. and has delivered high performance every time at a very high level.


I have never had the Engine Cases open since I acquired this Engine/bike many years ago so felt it is the perfect time to do a complete engine rebuild to get the bike ready for all the upcoming events in 2018 and forward. I will be taking no short cuts on this rebuild and using only top quality parts and services!



The bike did experience an oil failure in Beaver UT on the next to last day of our event and had a soft seize on a big climb up the hill.

This image is hidden for guests.
Please log in or register to see it.

Upon further inspection it was not the oil pump it was a blockage in the Oil Tank/Main oil line... So will be looking inside the oil tank to see if/remove screen from bottom drain and adding an inline filter to avoid that in the future.

I also discovered once I pulled the Stator and Main Seal that the Main Bearing on that side was completely free/spinning on the Crank Shaft... now appears after some Caliper measurements the previous person who was in there honed out the inside race of the Main Bearing to allow it to slide on easily I guess???? What??

This image is hidden for guests.
Please log in or register to see it.

So- new parts are ordered and cases are now split and the cleaning will be begin today. Will be sending off the Crank to Bill Bune for a complete rebuild and Cylinder and Piston is going to Enduronut to get it his expert opinion on what might be needed if anything with the cylinder.

The Widow is going to be even better and will be awesome to have a complete new rebuilt engine underneath me!

Progress so far....

This image is hidden for guests.
Please log in or register to see it.

This image is hidden for guests.
Please log in or register to see it.

This image is hidden for guests.
Please log in or register to see it.

This image is hidden for guests.
Please log in or register to see it.

My opinion in the light seizure is that it isn't caused by a oil restriction but probably by a lean spot at light throttle cruise , probably needs a tad bigger pilot jet ( determined by air screw position) or maybe raise the needle a bit. . The engine needs to blubber a little at that throttle opening

Rich

One of the interesting characteristics of the RT1-360 (piston port) is they are very difficult to seize......
never actually seen one hard seize. These motors will tolerate a lot before
even soft seizing. I ran mine with very very little oil for over 400 miles when the drift pin fell out of my oil pump.

A slight lean condition off throttle will not soft seize an RT. Greg experienced almost total oil starvation at highway speed ....
IMHO most 2 strokes would have hard seized at this point !

As Greg found the motor "tightening up" on a big hill and he pulled over.

He added some oil to his gas tank and was able to continue his ride back to camp .....a testimony to how tough an RT truly is !

The Yamaha RT1 is not your typical machine......

Fortunately it takes a lot more than an off throttle lean condition to seize an RT!

I would be curious if ANYONE on this forum has actually hard seized an RT1 ?

Yeah I run a 60 pilot jet in this bike with the needle 3rd slot down from top- and sure do like for all my bikes to have that blubber at start of throttle as Rich describes below.

As Dave detailed this was a total/complete oil starvation for most of the day. I usually always drop a little extra 2-Stroke (Castrol) oil into my gas tank because I like the sweet smell but most important to give the bike a little extra protection...

So the first part of the ride on Saturday was ok as I had a full tank of fuel with some oil but as we continued thru the miles and additional fill-ups it was getting less and less.

I am amazed with all the Highway riding and long dirt roads we took on that day and then to take on the Extreme straight up rough trail we headed up along with that final big push up to 10,000 ft the bike then started to tighten up and was able to shut it down immediately.

Once pulled over kept kicking to keep the piston moving while letting everything cool down. Pumped a little oil from the oil tank into the gas tank and after a short period she fired up and got me back to camp running as good as it has every ran. No Smoke but ran great for the last 30 miles.

Zero appearance of any damage now that I have it all tore down other then some very minor piston scuff on the sides.


Agree these RT1's are as tough as nails and just goes to show you how much extreme these engines can handle. Will be awesome to have all new bearings and fresh built crank in there now!

So, you had a blockage at the bottom of the Oil Tank...I take at the 'fitting'....w/a screen being in the fitting screw?

..And, if that's correct, you'll now bypass/or remove that screen?.....and add an in line 'fuel or oil' filter....?(please clarify) ...somewhere between oil tank and pump.

And, just a thought, would it not be beneficial to replace the black rubber supply line with a 'clear' one? Not oem, but then you really might be able to spot
a blockage, and at what point...?