My 60th birthday present

[Mailman]

gggGary,
yes to new float valves.
No to leak testing the floats. I should've I know.
There is no indication of overfilling the carb bowls. And for what it's worth I spent a ridiculous amount of time measuring float height.

 

[TimeMachine]

Was Your timing advancer serviced ? 5twins recommended and I say definately clean & lube cuz its So Ez and Free ! RT

 

[retiredgentleman]

I agree with 5twins.....................the carbs must in sync and the ATU must be working correctly.
I have found a very good way to do a bench sync is to use a slip of paper as a feeler gauge. You adjust the butterflys until there is equal drag under each butterfly. As part of that you must also check that each butterfly can close fully, i.e. butterfly not binding on the carb body. Using this method will get the sync very close, and then use a manometer to do the final check.

With BS38 carbs that you have, you need to check the rubber O-ring used on the needle jet. If its worn out, unmetered fuel mixture can cause a high hovering idle.

A common cause of a high hovering idle is air leakage around the carbs or carb manifolds. Worn out throttle shaft seals will allow extra air to increase the idle rpm. If you do decide to replace the throttle shaft seals, buy them from Yamaha, not from Mikesxs. The OEM seals work properly, while the aftermarket ones don't.

 

[Mailman]

I have found a very good way to do a bench sync is to use a slip of paper as a feeler gauge. You adjust the butterflys until there is equal drag under each butterfly./QOUTE]

I saw this suggestion of yours in an earlier post and I did exactly that. It's a very good idea and gets you closer than you can see with the naked eye.

"use a manometer to do the final check."

Yes, I need to construct one and and get some vacuum ports installed in my carbs.

Also, all o rings , gaskets and seals were replaced with New when I rebuilt the carbs. All parts came from Mikes XS. I was pretty new and hadn't read much yet about some of the sub standard parts out there yet. I also continue to be amazed at all the new and NOS parts still available for these old bikes.

 

[Mailman]

Was Your timing advancer serviced ? 5twins recommended and I say definately clean & lube cuz its So Ez and Free ! RT

Not yet, doing that very thing next!

 

[MaxPete]

Pm sent.

 

[retiredgentleman]

My throttle shaft seals, from Mikesxs, only lasted 2 seasons before they started leaking air again. Replaced with Yamaha OEM
part # 256-14997-00-00, and they have been leak free for the last 7 years.

 

[5twins]

When I work on one of these for someone, one of the first things I check is the advance unit and advance rod if so equipped. 9 times out of 10, I find them all dried out, sometimes even rusty. The last one had the advance unit greased but the advance rod was dry as a bone. I guess they weren't aware that needed "lube love" too, lol. There's no sense even messing with your timing and points unless the advance stuff is squared away first.

You can easily access these parts without disturbing your points or timing settings. Remove the 10mm nut and little disc on the advance side and pull the rod out the points side with the points cam still attached. For a first time cleaning of the advance unit, I usually remove the weights from their pivot posts so I can thoroughly clean and lube them. But, I don't recommend this unless you have spare e-clips on hand. The originals sometimes break during removal. Once cleaned and lightly greased, I keep the pivots lubed in the future with just a little foaming chain lube. I apply it after a ride while the bike is still warm/hot so it penetrates better.

There's only one little "gotcha" to doing this service. You have to have the advance rod installed properly or it will throw your timing off 180°. Yamaha helps you here by placing scribed alignment lines on the parts. Here they are marked with the yellow arrows. They must point to, or nearly to one another .....

 

[Mailman]

Thanks 5T! That's very helpful. Your archive of photos really help people like myself understand a technical discussion. Much appreciated!

 

[5twins]

Here's a few more. Once the advance rod is removed, you'll be able to see the bushings in each end of the cam. The outer bushing on each side has grooves cut into it's I.D. These are to hold grease and keep the rod lubed .....

Clean them out and pack them full of fresh grease. Yamaha recommends a grease with moly in it. I use VW CV joint grease because it has a very high moly content .....

Besides the alignment slash marks shown above, there's another way to check/insure your advance rod install is correct. The little disc on the advance side mounts on a locating pin in the advance rod. There is one on the other end for the points cam too. These pins should point in the same direction .....

 

[Mailman]

Thanks again! This is all very helpful. This is good reference material. I will definitely do that.

 

[5twins]

Although the manuals don't mention it at all, this is required maintenance on these bikes. But, you needn't do it often, maybe only every 6 to 8 years. Freshly greased and filled bushings will keep the advance rod lubed at least that long, probably even longer. Consider the fact that most of these never were re-lubed since they left the factory. Just now, 30+ years later, are they starting to bind up.

 

[Mailman]

Today, first a joke.
A little boy was watching a blacksmith making horseshoes, the boy moved closer to the pile of horseshoes, curious, and the blacksmith said " careful they're hot."
Pretty soon the boy picked up a horseshoe and quickly threw it down. The blacksmith said " burned you didn't it?"
The boy replied "No!, it just doesn't take me long to look at a horseshoe!"

I am like that boy, offered good advice that I chose to ignore.
Last week when I started my bike the throttle was hanging up, revving too high and then slowly coming down. To try and remedy that I worked on two things today.
The first thing was easiest. Weeks earlier while working on my bike I had all the cables and wires loose. I knew I didn't have some of the cables ( including the throttle) routed properly but I was just guessing where they were supposed to be. Well I found a diagram in a factory assembly manual. So I pulled the gas tank and got my cables in order.
Then I started working on the advance rod. Being advised that they get gummed up and hang up in the advance position.
With 5Twins warning ringing in my ears " Don't remove the E clips that hold the advance weights unless you have spares because they are prone to break."
Well I thought that everything needed a good cleaning so...
Ha! I said to myself, maybe a rookie might break one, not somebody careful like me. SNAP! Crap!

So a run the the hardware store tomorrow, hope they have them or I will have to order them online. Which brings up a question. Is there some special technique for R+R ing those clips? Seriously?
Anyway, once I removed the weights and springs you could see rust on the pivot shafts and when I pulled the advance rod out you could see there wasn't a speck of grease where the bearings are , also the advance rod had old gummy, sticky grease on it so I'm glad I got in here.

So I cleaned everything up and greased the pivot shafts, cleaned and oiled the springs, filled the bearing areas on both sides with moly grease and reassembled.

So now I just have to wrangle up some E clips and finish this. Unfortunately until I get them I can't start the bike to see if my fix worked.
Well there is always cleaning and polishing. Hey gggGary, look what came in the old mail box today! I can't wait to try them!

Until next time. Bob

 

[TwoManyXS1Bs]

Years ago, I welded up a modified clutch lever/petal bracket for a friend's '68 Mustang fastback. Finished, it's setting on the welding table, still glowing red. He does a full palm grab of the thing. (*extremely loud noises follow*). He still has this ' branding'.

Gunsmithing shops usually have a variety of those small c-clips...

 

[Mailman]

Years ago, I welded up a modified clutch lever/petal bracket for a friend's '68 Mustang fastback. Finished, it's setting on the welding table, still glowing red. He does a full palm grab of the thing. (*extremely loud noises follow*). He still has this ' branding'.

Gunsmithing shops usually have a variety of those small c-clips...

Haha! I feel your friends pain. I was a welder for ten years, burns and scars come with the job!
Thanks for the heads up for the c-clips.

 

[MaxPete]

One thing is for sure - when you get this bike done, she is going to be VERY nice indeed.

Pete

 

[Mailman]

Thanks Pete. I'm sure trying. A lot of this work is completely new to me, I'm a little out of my comfort zone, but this site and its members are such a great resource and everyone cheers you on. I'm having a blast! I can see why you started another project!

 

[5twins]

That clip is something I keep a good supply of. Besides breaking, they often zing off into never never land never to be seen again, lol.

 

[Mailman]

Thanks 5T , I was wondering what size they were and where to source them. Much appreciated.

 

[theDQG]

This has been a very informative thread. Following. Keep up the good work, Bob.