Newbie wants to learn

Hi to all....I'm new to the motorcycle world, but I can turn a wrench and use a search button, and I want to learn the right way.

Long story - short...I bought a '82 XJ 750 Maxim with about 28K as a project (in other words it's not running)....all outward signs say the bike was well cared for (it's clean), according to the P.O. bike was running fine until this Spring, at that time it would start fine, but once he started riding it would bog and die (10 - 15 mi.). This got progressively worse, now IF he can get it started it'll go 2 mi. tops.
I'm taking delivery on Friday (he accepted $250)...What would you look at first?
My thought is fuel delivery.....if it starts and runs it's got compression (will check), it's got spark, and it's getting fuel, but the system is clogged so after a period of time dry.
I've spent the last couple of night looking through the site, hoping this is a common problem with an easy fix....maybe some of you could get me going in the right direction

Thanks

Pat

 

I'm thinking rust in the tank, clogging up the carbs is a strong possibility. Pull the tank, drain it and check the fuel....probly lead to carb cleaning. Once you get it running then you can move to valve lash tolerances and things like that.

A service manual will be your friend too.

 

Hey there, Im new too. I just picked up my bike on tuseday! Im in the same boat as you where my bike wont run. This forum will be a crucial part of getting my bike running. Ive been told that even if your fuel delivery system is in working order you need to make sure you valve clearance is good. Fitz seems to be the know it all guru around here so listen to anything he has to say.

Welcome for another newb!

 

Here is the list:

1. Valve clearances: get your valves in spec if they are not all other work done is in vain. You will never get a good synch on the carbs and the bike will never run right. Chances are this has NEVER been done and should have been done at 3K and then every 5 or 6K. My Haynes guide says 6K for valves but 5K is the number used here most of the time.

2. If it has been sitting you will most likely have to clean the carbs and do some work on them. Ethonal turns to varnish after a period of time not good for the tiny passages in these carbs.

3. Check that the vacuum tube is indeed a vacuum tube not a piece of fuel line or something else when it gets warm it will start collapsing on its self.

4. Rear brakes, you have to check the rear shoes for delamination. Some of these bikes are sold with 30 year old rear break shoes. They are ticking time bombs. They will come unglued and lock up your rear wheel, something you don't want happening at 75 MPH.

5. Break lines check the date code most likely it is a rubber one and needs to be replaced.

6. rebuild the master cylinder, chances are it has NEVER been done.

7. Compression test just because you get fire doesn't mean you have good compression.

8. Petcock: these bikes have a vacuum fuel system your petcock has three settings ON PRI RES. On is well on, PRI is Prime use this to fill the carb bowls if they are empty. Do not leave this setting on for long if you have a sticking float you will end up with a crank case full of gas. Res is your reserve. But a XJ750 has a 4.1 gallon tank total capasity. With a 1.1 gallon reserve. on my 650 I get about 156 miles before I hit my reserve.
On the petcock there are two tubes the top is the vacuum tube the bottom is the fuel line. I would suggest installing or replacing any in line fuel filters.

9. Get a new battery or at least have the current one load tested, they will do this for you at just about any auto parts store.

10. Tires, check your date codes you could have dry rotting rubber time bombs on the bike.

11. New oil and new oil filter.

12. Inspect front breaking system rebuild unless the PO can prove beyond a shadow of a doubt that it was done in the past two years. Honestly I'd go it out of GP to be safe!


I am sure I've have missed a few things for you to check before you THINK of riding this bike.

I think if the bike is dying out after a short time I would look at the vacuum tube and battery. But really that list above should be completed before you even think about riding this bike!

 

Valves first! you can clean and synch carbs to the cows come home, if the valves are not in spec your wasting your time. That is simply the stone cold hard truth.

 

Never mentioned sync Doc but I'm not gonna waste my time screwing around with valves until I know the bike runs and has at least some forward gears.

 

You'll never know if it runs (or is going to) run right until you get the valves in spec. It's not "screwing around" it's the very important first step in being able to even test the viability of the motor. You can't even do a valid compression test if the valve clearances are way off.

 

OK, it will take you like an hour to check the clearances max. Here is a how to http://xjbikes.com/Forums/viewtopic/t=14827.html

I will say this now and others will chime in, these XJ bikes are a little different than other bikes. If the valves are not in spec you'll not get anywhere with them. I've seen 100's of posts here where people refused to do the simple thing and get the valves in spec. And in the end they just get angry, they spend the hour to check the valves get the correct shims and install them and guess what their life gets so much easier. I assure you, doing the valves is much easier than cleaning these carbs correctly. You can't simply drop them in to a bucket of carb cleaner it isn't going to work.

So, don't waste your time, no wait you will be wasting your time. But what do I know. I am pretty new to this as well. I only have a running 82 XJ 650, that purrs like a kitten, gets 45.88 miles to a gallon.

You asked for advice, I am giving it to you and trying to show you what you NEED to do..

 

Brothers and sister, we have here once again a doubter. One who does not believe in what we all know is to be true. Valves are where you start with these bikes. Now brothers and sisters, help me show this wayward XJer the light! Help me show him the way of the XJ. Others have not believed in the past then they do this simple work and the darkness is lifted from their bikes and they begin to make progress in getting it to run!

 

I just re-read the original post. Symptoms like those can indeed be caused by tight valves, too. Remember that tight clearances get even tighter as the engine warms up. A valve at zero clearance that closes "ok" when the motor is cold may very well stop closing completely once it warms up, even a little bit.

You cannot assume "it's got compression" without testing the compression.

If you get weird results, then check the valve clearances; put in spec, and re-check the compression.

Like I said in my response above, it's part of diagnosing a motor effectively.

 

Doc, think you got your guys mixed up!

Patmac posted the original question, not me....I'm not asking for any advice. I've been working on my own bikes for the better part of 50 years and am very comfortable with my time proven procedures.

 

Opps sorry... I see where I got confused my apologize..

 

No apology necessary Doc!

Just reading the guys first post...in this instance...I may tend to believe the previous owner when he describes how the bike quickly went from running well to only going a couple miles before stopping.

It's easy enough to prove....just dump the gas out and look for rust particles. More than likely there will be some.....BUT, that is definitely not the end of the story!

I'd also place a buck or two on the valves being never touched and they too will need checking/adjusting.

I just like to hear them run first....personal preference I guess....anyhow everything's good!

 

Doc when are we going for a ride??? My bike is ready!
These guys know these bikes well. BigFitz helped me get mine running much better than it ever had run before. I'm still tweaking and adjusting as I'm learning. You may think the bike runs well, but in most cases it doesn't. I've put on new tires and brakes and wow what a difference. If you think it is any myth that running old tires is unsafe it's not. My bike gets better and better the more I read on this website, and go and tweak on my bike. It's getting to be lightning quick... and it wasn't that way when I bought it 10 years ago with 5500 miles on it! These guys rock!

 

We had a member bought what he thought was a decent-running, low mileage 550 Maxim. Started and ran, seemed a bit down on power. But it started and ran.

TWO PISTONS were HOLED. No crowns left.

These little fours are so strong they can fool you. Hearing one run is no guarantee of anything.

 

Could also he gas cap vent. But you have to check the other stuffs 100% too, just an alternative idea.

 

Holy Crap!!! I didn't mean to kick the hornets nest!
I just want to #1 get the bike started and warmed up....maybe ride it around the block a couple of times and get a feel for what it's doing, rather than rely on P.O. opinion.
As I said in the original post....I think it's fuel delivery that's causing the no start/bogging issue, but until I can actually get my hands on it, it's just a guess.

I'd bet the farm that the valve have never been checked, but if I must be truly honest, I've read the valve clearance posts, and have gone over it in my Haynes manual....the checking part seem like something I could handle, but the part about readjusting them...getting the right shims and all is a little intimidating! I hope there are some patient members here!!!

 

When you get ready to actually do the adustment, post your clearances and installed shims; and what you think the substitutions should be and we will gladly "check your work" before you order any shims.

 

Hahaha!! Believe it or not patmac, we're all in agreement, just have different ways of wording it!! :lol:

 

Well I guess it's just gotta be done....

Where do you suggest getting the clearancing tool? How much are they? Are they every up for sale....used?
Where to buy the shims?
Better yet....where do you guys buy your parts....on the automotive side I usually get my stuff from RockAuto.com .... high quality, inexpensive, and fast delivery (at least here in WI)....the "stealership" is just so expensive.

Like I say....just want to learn.....

 

XJ4ever.com has everything you need. His generic valve shims are high quality, and he has the valve tool, and meteric feeler gages.
Better plan on getting a new valve cover gasket and donuts from him too, you'll need it. I went gerneric here as well with no problems. He has quality parts with fast shipping. You won't be disappointed.

 

For parts for the bike most of us use the contrubiting vender XJ4ever. PM Chacal and he'll get you a quote the valve bucket tool isn't that expensive, others might be able to tell you where you can score one as well. Honestly it is hard to beat their prices on new parts. I've looked and tried and couldn't do it. Shipping is very fast with in the U.S. I'd say 90% maybe more of us here order parts and specialty tools from XJ4ever. Chacal is great about making sure you are getting the correct part, for your bike as well.

sorry if I came off hard line on you. We've had a few new uses lately ask for help and then flat out refuse to do what we suggest and keep asking what else could it be.

Honestly, the valve cover gasket may be the factory installed on, you may want to order the valve bucket tool, new gasket and 'donuts' pressure washers all at once. I have a feeling all of them are most likely cooked.

 

I am free Sunday! PM me we'll work it out!

 

Honestly so do I. But in the case of it isn't running why not trouble shoot from top to bottom? I am a I.T. professional and I've learned over the past 20 years to start at step 1 and progress from there. It seems to me on these bikes step one is the valves. So if the bike isn't running might as well knock that issue out first. And really to dump the fuel out and check the petcock screen for gunk, you have to remove the tank anyway you're half way there at that point. And with Bigfitz's guide, it is pretty simple to check them. I mean it took me two hours my first time. But only because I kept referring back to the guide to make sure I was doing it in order and step by step as laid out by Bigfitz. I think it took me an hour and change to put the new shims in and make sure the valves were in spec.

I agree hearing/seeing them run first is great. But on these XJs if it isn't might as well do the valves first because if you are coming here for advice the first thing everyone says is "Are your valves in spec?"

 

If you want to take the time to do it right just pretend you're a drop of gasoline traveling backwards through the system.

Start at the spark plugs (replace) and travel back through the motor
Next step would be valves check/adjust
Then carbs (clean/sync)
Fuel line (replace)
Fuel filter (install/replace)
Petcock (inspect/rebuild)
Gas tank (bet it's got some rust)
also charge the battery and take it to an auto store

93% of the time if you do all of these, the bike will start.

But that doesn't mean it should be ridden,

 

Hold on a minute here. You get a new2 u bike that isn't running just right or you just feel the need to do something to it but you read here that a running sync is a waste of time before you do the valves, wrong.
At least try, 1 or 2 sizes won't kill it instantly and codnsider the service interval is like 5000 miles but a PO can mess up a sync in 5 minutes. You do need to set the valves but there's no sense in stalling and idleing at 3k till you do
At the very least it's good practice.

 

It sounds to me, based on the symptoms patmac described, that the bike was running fine and a short time later (riding time) the bike won't go over 2 miles without quitting.....His question was "What should I look at first?"

This is not an issue of whether or not valve lash check/adjustment is an important and necessary maintenance procedure, or what is the best way to approach restoring this bike to peak performance, or even what oil to use....it's simply.....where will he most likely find the source of this particular problem.

So....to answer his question, in my opinion, his best bet is to dump the gas out and have a look....the second thing I might do is Polock's suggestion and look at a running sync, it would be tooooo easy for a 'helpful buddy' to say to the PO...."I've seen this before....you just need to turn these screws a little!"

Will the valve tolerances need to be checked before riding the bike any distance....of course, but they aren't likely the source of this problem, as described.

 

Equine Plumage.

One or more dead-tight valves COULD very well be the cause of this symptom.

There is only ONE WAY to completely rule that out as a possibility; and it isn't just saying so.