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1976 tt500 won't start!

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It kinda suckks, i already had this thread made and we were getting somewhere but looks like we get to start over being that the thread was deleted and my account was gone, probably because of the forum change. Oh well!

I just got a TT500 a week ago from a buddy. I had it running and started it many times and drove the heck out of it for 2 days, then i was riding it and it started backfiring, and then started to die when i let off the gas. So i held the RPM's way high and as soon as i let the RPM's drop it died. Now it refuses to start.

I have gapped the points at .014 and have timed it to start opening the points at Fire (F). I also gapped the spark plug although it was almost dead on.

I put it in second, roll down a big hill, pop the clutch and lunge on the seat, and the wheel just locks. Before i could walk with the bike and pop the clutch and it would fire instantly.

So... It won't try and start AT ALL. not a pop, not a kickback, not a puff.

It is timed, points gap is at .014, spark plug is gapped and brand new, i checked for spark at the plug and it is getting a nice blue spark, and i when i pulled it, it was wet so it has to be getting fuel right?

And, i have checked the valves and adjusted. .003 intake .005 exhaust.

Would it have trouble starting if the jets in the carb were plugged, even though it is getting gas due to the spark plug being wet (i also kicked it over with the spark plug out and shot gas out)?

What if i take off the supertrapp, a buddy said his bike wouldn't start at all and a guy came and told him to take the supertrapp off and it started instantly.

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I finally found a problem (THE problem?!?!)

I pulled the spark plug to check for spark today and the coil plug fell apart in my hand... big problem right there! So i ghetto rigged it. Got out the electrical tools, and spliced the coil's plug wire into the plug again. Put it back on the spark plug, kicked it over, NO SPARK!

So i had/have a bad plug (temporarily fixed) and i have no spark! So then i pulled all the wirse apart on the bike and cleaned contacts. Then checked for spark. I got spark! For about 3 kicks. Then the spark went away. Interesting....

So the bike has no spark, or it does for about 3 kicks then it's gone. Time to buy another $40 used coil???

What i need to know... is how can i check to make 100% sure the coil is bad before replacing it? When i put the electrical tester positive wire in the coil's power wire connection and set the tester on 20v, i get a ready of about .6, sometimes a little smaller, when i have someone kick it over. My electical tester sucks though you have to wiggle the wires... but is that about what it should be getting?

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This is a coil off my 83 XT250(6V)

Good

P1000702.jpg

Bad(actually a bad plug cap, but you get the idea)

P1000703.jpg

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Thanks for the pics! Thats the exact test i need to do, with and without plug end too!

But the problem is my tester doesn't have that symbol you've got yours on. Mine's pretty similiar but it doesn't have the one thing i need that you have there..

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I would think you should have an ohms setting as most do, what you're checking with this setting is resistance.

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It's not getting fuel now. Has a great spark (checked the coil and it's good apparently, I wasn't kicking it over hard enough when i was checking for spark with the plug out! When i kick it like it should be kicked it has a great big spark.

But no fuel now... which is probably the problem all along?

I pulled the carb off, shot air through everything, shot air through both jets (there was a bunch of junk in the main jet tube that i blew, but im not sure where the dirt exited, if it did...

And then i put it back together and hooked it up to the gas tank. When it is full of fuel and i am opening the throttle, full throttle 20 times with my hand, shouldn't there be fuel squirting out of it towards the engine's intake? No fuel whatsoever comes out of the carb when full of fuel and i am pumping the throttle.

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Did you check the petcock filters? How about your gas cap venting? If your carb was as dirty as you say I would definately go through it again, may not be a bad idea to rebuild it.

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You posted the same q in the jetting area. Your carb has no accelerator pump.

You stated when you pulled the plug, it was wet, so fuel or other liquid is getting in.

I would drain the fuel into a glass container and inspect it.

If the carb is clogging up quickly, you need to remove all the contaminants and replace the pilot jet, if not all as cleaning is often a waste of effort for most people.

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MEANDMYDRZ... I actually took the carberator apart once more for the last time. I COMPLETELY took it apart this time! I cleaned everything... There was no dirt anywhere in it. Cleaned the jets, floats, float pointer deal (not very good with carb part names) that it pushes on when the float moves, removed the slide cyclinder, cleaned, cleaned every passage way, etc.

put it back together and installed. Kicked the bike... and guess what, the first sign of life in a week. I got a HUGE backfire. Loudest i have ever heard. Probably scared the neighbors.

Then i pushed it to the hill, rode down and popped the clutch in second. I was thinking that it was actualyl spuddering but it might just be the piston moving fast since i'm getting some good speed... it's hard to tell.

So it should'nt be the carb anymore, i thoroughly cleaned and checked that sucker. You mentioned gas cap? Are you saying make sure it isn't plugged? It is definately clear because i keep forgetting that the tank is full when i lay it down and it spills out the vent.

I even sprayed starter fluid in it today and it still wouldn't do anything. Spark + fuel = no start? how!?

William1... Thanks

Yes i posted a quicky in the other section because i was "rebuilding" the carberator at the time and thought that there had to still be something i missed that was clogged because fuel never squirted from it... turns out im just too used to car stuff.

The fuel is brand new, 1 week old now.

I'm double checking my valve setting right now.

I appreciate all the help, sorry it's so confusing, i know it has to be for you guys because i don't even know what the heck is going on with this bike!

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Only slightest chance of a problem i have found after looking this thing over 100 times is that the points spark is sparking just after it opens, and not at the full .014. Is it suppose to be like this, or should it be sparking at the full .014?

One other thing. Maybe two. How should my idle be set? Should i turn the idle adjuster knob so that the slide is just barely cracked open? or should i open it quite a bit? It was open a lot, until a few minutes ago i set it so it was just barely above closed.

The other thing. Air adjuster screw. Mine was 3/4 out, i read somewhere it should be 1.5, so i adjusted that. I also read that there can be an air leak in the intake rubber. I tightened that. ALl of this... still not a puff.

Edited by 1976tt500

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Actually, the spark occurs just milliseconds before the points open. As they begin to separate, there is a voltage drop, this causes the magnetic field in the coil to collapse, inducing a charge in the secondary, high tension circuit thereby making the spark.

This is why, when setting points with an ohm meter, you set them to the point where the resistance changes (increases), not when it shows as a fully open circuit.

Ball park setting for idle eyeballing is about 1/8" opening.

Fuel screw base setting is 2 turns.

Think basics.

Good spark?

Fuel - Both good quality and actually getting in the engine

Valves, clearances right

Compression.

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Okay thanks for the info. I adjusted the idle screw so that it basically wasn't affecting anything because i had it so the slide came to a stop. I'll open it up just a little.

When you are saying fuel screw is that the same as the air screw? I thought it was an air screw that let a little bit of air around the slide for idle, when slide is closed.

The basics

-Fuel is fresh, higher octane pump gas (92). But now that i think about it.... I was riding the dirt bike around all day, when i ran low on gas. I had no gas, but a fellow race team had several 11 gallon dump cans that they wern't going to use because they bailed out of the race. So they let a buddy and I siphon gas out of them into our bikes. Well I got a few hundred feet from the siphon spot, when it died. Interesting.... I'll replace gas just in case but it seems perfect to me!

-Fuel getting into the engine.... I'm thinking it's not. Because if it was... how could there not be combustion with my good spark. But what can i do about this and what can i check? The carb is 100% cleaned out, so it should be vacuuming into the engine, right!?

Valves- i double checked them yesterday. They are set on compression stroke, at TDC. .003 intake .005 exhaust. Cold of course.

Compression. I need to check this, but i did the cheap quick not accurate but helpful test of putting my finger over the spark plug hole and pressing as hard as i can while someone kicked it over. I was unable to keep my finger on the hole during compression while kicking. So it does have atleast decent compression.

THanks. I am getting close i know it.

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Just compression tested it. 50psi. There's my problem.

Before i pull the engine out is there anything that i could possibly done wrong or could be set wrong on this engine giving it low compression? Such as the valves? If i have the valves set wrong could that be the reason for low compression?

The previous owner (my boss as well) said the one thing that he knows about the bike, is that the bottom end is in great shape. And why would the bike run and start perfect then lose compression all of a sudden while riding? These things just make me think that I'm doing something wrong. If valves can affect compression outcome then that has to be it.

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/ End Thread. You will notice a new thread very shortly, of a TT500 frame off restoration.... yeah, 45 minutes ago i decided im just going to do the frame off restore on it early. And now, The bike is stripped down to a frame, and front and rear suspension. The engine is sitting next to it.

Anyways this thread should be great help for anyone else trying to start one of these beasts... we went over everything in this thread and it came to the worst posible outcome.

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haha yep... I'm not going to let the thing sit, in a non running state with no compression. ANd I'm not going to sell it because it's already grown on me, and i've put $200 into it already. I could of stopped after pulling the engine, and rebuild the engine or replace valves if it's the case of a burnt valve. But I have been dreaming of restoring this thing ground up for the ultimate pit bike at the races, and very well could be the prerunner (cruise the 60 mile desert course and note any dangers and such). So why fix the engine and put it back in when you're already 1/4 way done tearing it down🤣

It was funny when I tore the bike down to bare frame in 45 minutes and my dad (I'm 16) didn't know i was going that far with the bike, walked into the garage... 👍

Bike won't start. What do i do? WELL......

june9047.jpg

I have a restoration thread up now to further discussions...

Edited by 1976tt500

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