Modern dirtbike front end on old Yamaha Enduro

billy mild

New Member
xb33bsa said:
then show some respect for you're family.don't fucking ruin it :-\ which is what you will end up doing trying to make it something it is not
If that was the reasoning of everyone then this site wouldn't exist. Think about it.

I'm just trying to make the bike safe. The fork legs are way too small to take any kind of abuse. I also would like to add a disc brake in order to help with stopping.
 

mydlyfkryzis

当有疑问时踢你的敌人在生殖器上,你可以道歉后
billy mild said:
If that was the reasoning of everyone then this site wouldn't exist. Think about it.
Have to agree with XB here....The site would exist, BTW, but with fewer ruined bikes. Too many mods are just not really, say, "well engineered?"

Good upgrades are O.K., but some people end up with beautiful, unridable, or non-running bikes. If it is a family heirloom, why would you want to abuse it? Ride it gentle, have fun....

Remember, if you improve the forks, the frame is not stronger, so that will need to be improved. Many of these old bikes do not have the frame strength and engine that would warrant modern forks and suspension. Modern bikes use stiffer frames to handle the more compliant forks. the frames were originally designed to flex to absorb some of the pounding. When making majoer suspension changes, you often unbalance the bike. A strong fork on a weak frame rarely helps matters.
 

billy mild

New Member
mydlyfkryzis said:
Have to agree with XB here....The site would exist, BTW, but with fewer ruined bikes. Too many mods are just not really, say, "well engineered?"

Good upgrades are O.K., but some people end up with beautiful, unridable, or non-running bikes. If it is a family heirloom, why would you want to abuse it? Ride it gentle, have fun....

Remember, if you improve the forks, the frame is not stronger, so that will need to be improved. Many of these old bikes do not have the frame strength and engine that would warrant modern forks and suspension. Modern bikes use stiffer frames to handle the more compliant forks. the frames were originally designed to flex to absorb some of the pounding. When making majoer suspension changes, you often unbalance the bike. A strong fork on a weak frame rarely helps matters.
I thought upgrading the front forks to a little bit more modern of a setup would allow it to handle better and stop better. Along with upgrading the front I would put some new shocks on the rear. All of this would make for a better all around bike. I would keep the original parts so if I ever wanted to go back to stock I can.

There are always ways to improve on the OEM design. I'm not trying to change everything on the bike, just update a few things.

Maybe I will just update to the DT/RT front end on this bike and just be happy for the larger drum brake up front. The motor will be getting a update. I just wanted the rest of the bike to be able to handle it.
 

DesmoBro

Busted Nut
Sometimes when your building a bike (photoshopping) and you need this $60 bearing....but there is an entire whole other bike (project) for $75 so you get that and it needs (piston) $80 but you watch 100 you tube videos anyway and watch the world fastest indian ......and subliminally......you sandcast your own piston in your sleep.....
 

mydlyfkryzis

当有疑问时踢你的敌人在生殖器上,你可以道歉后
I am not saying don't improve it, only that really big changes often do not have the effect you want.

For instance, when I was younger, the common upgrade to a car was to put overload spring shocks on, to lift the back and stiffen the spring rate. It looked and worked cool for the first few days, until the shock mounts broke from the added stress.

Ever see the lowered Honda's, bouncing their suspensions against the stop. Destroys the suspendion arms and bushing pretty quick. Lowering a car needs more engineering then cutting a couple of loops off the springs.

Same with the bike. The frame is flexible, the frame size and strength were designed around the forces that the forks provide. So when you hit a pot hole, the forks flex, absorbing some shock, and the steering neck moves a little. Now upgrade to a much better fork. Thicker, stronger downtubes, stiffer valving. Now when you hit a pot hole or bump, the fork do not flex, sending much more force to the steering neck. While it probably won't snap "today", the increase forces and flexing will fatigue the welds around the neck and possible cause a failure of the steering neck.

I am not guaranteeing this, only saying there is more to improving the bike than just stiffer shocks and a bigger fork....You have to look at the whole system. Some bikes are over built, and the upgrade is within the ability of the system to handle it. But most bikes are not so robust, so changes like that have unintended consequences.

That's why stuffing a 350cc motor in that 100cc frame doesn;t work...the frame can't handle the power and torque....

XB is very knowledgeable and experienced, and as full of finess as a 5 lb sledge....but he is pretty much on the mark.

Try another method. You would be surprised how much better a bike handles when the wheels are true and spokes properly tightened. I know from my own bike, the single biggest improvement from handling came not from tapered bearings, right size tires, new bushing in the fork, but from straight wheels with strong, properly tightened spokes. I neglected getting that right in the past and fought a wobble for years.

Get the steering stem right, forks straight in the clamps, true and tighten wheel spokes, it may surprise you at the improvement. Have you ever checked the wheel run out?
 

billy mild

New Member
I understand what you are saying. I am familiar with suspension setups on cars.

My wheels on the AT1 have not been looked at, and that sounds like that might be out of my domain to be able to do that. I need to get the suspension sorted first. My rear shocks are blown, the front forks are leaking bad(hence why I'm looking at newer options). Once I have that sorted then I could get the wheels looked at.

The bike was used as a weekend trail bike back in the 70's, and as a daily commuter for my dad in the late 70's. So the bike has a ton of miles on it. I started riding it when I was 13 and rode it for a few years with little to no work done to it. I added a GYT kit pipe and jetting to match as well as replaced the air filter with a K&N. The engine actually runs decent for having all the miles on it. The autolube injection still works. The suspension is just tired.

I had a CL350 as well that I did some slight mods too. It had a 2 into 1 exhaust, pod filters, and cafe bars. I also rebuilt the front forks, and put some airshocks on the rear. It handle decent for being a 70's bike. This AT1 is terrible in comparison to that. I'm used to my RZ350, so riding this AT1 makes me leery of going at any rate of speed except putting around the yard. Maybe I will just rebuild my current front end for this season and look at newer options later.





Here are some pics so you know what I'm dealing with.
 

mydlyfkryzis

当有疑问时踢你的敌人在生殖器上,你可以道歉后
That is a nice little bike....Lots of room for improvement without being radical.....

I hope you have good luck getting it right.....

You don;t need to be perfectly stock, but close is going to be the least time consuming, and still give you a usable and fun bike!!
 

billy mild

New Member
xb33bsa said:
sweet even has the gyt kit pipe !
I put that pipe on there. It took a long time to find one too.

My plan for the bike is to make it look good, not sure a full resto is in order or not. My plans for the motor are CT1 cylinder and head, light portjob, bigger carb like a 28 MM instead of the stock 24 MM, and if the stock clutch can't handle the power, upgrade that as well. The bike runs and pretty good actually.

Do you see why I would like to slightly upgrade it a bit. I"m not looking to do inverted forks. Just a set of conventional forks with a disc front brake that would fit on this bike.
 

makotosun

Avoiding creeping perfection!
We have started a new website for the old enduros at www.Yamaha-Enduros.com where you can get good information, manuals, specs, etc. there is a forum for questions too.

I have a 1970 AT1 which is actually decent on the street (55-65 mph). It has stock front forks, just cleaned, re-sealed and fresh oil. The rear got some NOS Showas I found on EBay. I also added a stock DT259 steering damper.

 

noahwhelan98

New Member
I recently saw this post when looking for information on a fork swap for my 1970 AT-1. AllBallsRacing does not make neck tube bearings for AT-1's, but does make them for a 1970 RT-1/360. Would these work in my neck tube? I'm interested in an USD fork swap from a modern 85.
 

ridesolo

You only bear responsibility for your own actions
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I believe the best thing to do wold be to carefully measure your AT-1 neck tube. I've never called them, but have heard that they have a very good customer service unit. If you call w/ those measurements they may be able to answer some of your questions.
 

chickenStripCharlie

Been Around the Block
Another vote for you ain't gonna make it handle better. In fact, you might make it handle worse when you mess up the height of the front end and/or triple tree offset compared to the original.

It will look cool, though.
 

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