TBR7 Won't start

[Johnny_Sardine]

Hey, everybody.

So I just got two bikes. Hawk and TBR7.

Got them put together yesterday and Hawk started up but wouldn't idle. So I figured I'd throw the new mikuni vm 26 ito the TBR7 from the get go. I just opened it up and threw the 110 main jet, left the rest. Tightened the fuel mix screw til it bottomed out and let it out 2 1/2 turns as per motocheez' advice.

Bike just won't start. After a night of letting the battery recharge, I put the stock carb on there just to see what's up. Still no luck. So at this point I'm thinking it must be something else.

Battery is charged. Plug is sparking. Gas is flowing. Checked all wires and grounds for connection and tightness. Tried it in every configuration, with the kickstand up, down, break on off, clutch in, neutral, with the kick start. Shit man.

It has given me a glimmer of hope a couple times but really just a whole lot of nothing. I'm at a loss. And the frickin hawk just started right up.

The battery is doing a weird clicking thing. Not sure if it's shorting? Pulling the throttle will almost always cause the starter to stop with a loud click.

you can see what I'm talking about in this video



Any tips?

[Bruces]

Is the plug wet ? Have you tried dropping a little fuel down the spark plug hole replacing the plug then starting it ?

[NzBrakelathes]

Swap Hawk carb to TBR - what is the result? try swapping things till you find either Hawk won't go or TBR will go etc

[timcosby]

wonder if the choke lever goes the opposite direction. wouldnt hurt to try the other direction

[Johnny_Sardine]

This is what we did.

Swapped hawk carb we knew worked (but wouldn’t idle). Bike acted the same, no go. Switched batteries and plug from hawk no luck.


removed the gas tank. Rerouted spark plug wire, filled up the bowl of the carb Manually. Choke on, she acted like she wanted to start. Half choke, gas throttle and it fired up. Had to keep the throttle pinned to keep her running. Exhaust pipe got red hot. Sounded great until the bowl ran dry. Hooked the tank back and no luck.

Seems like the beast ain’t getting fuel. Valves??? That’s the only thing that I can think. Everything else seems to be there. Gas flows out of the tank.....

Thanks

[Megadan]

Yeah, adjust the valves if you haven't. Exhaust shouldn't be glowing.

[NzBrakelathes]

Originally Posted by Johnny_Sardine

This is what we did.

Swapped hawk carb we knew worked (but wouldn’t idle). Bike acted the same, no go. Switched batteries and plug from hawk no luck.


removed the gas tank. Rerouted spark plug wire, filled up the bowl of the carb Manually. Choke on, she acted like she wanted to start. Half choke, gas throttle and it fired up. Had to keep the throttle pinned to keep her running. Exhaust pipe got red hot. Sounded great until the bowl ran dry. Hooked the tank back and no luck.

Seems like the beast ain’t getting fuel. Valves??? That’s the only thing that I can think. Everything else seems to be there. Gas flows out of the tank.....

Thanks

So the issue is with the bike as swapping parts isn't helping, try adj valves and if you like or need check my eBay listings for a tool set to make this task easier.

If moving parts doesn't solve the issue and the Hawk runs fine and TBR doesn't after swapping common parts then it isn't the parts lol - does help with knowing where to not look lol

[wheel spinner]

ok... I'm going out on a limb here... but sometimes something sooo simple as the kill switch can screw us up... check the kill switch and test it... change the plug... smell for gas in the cylinder... make sure you got spark... choke it... then take the choke off..

[letsride]

SO, you have FUEL, AIR, and SPARK and you have adjusted the valves. First thing I would do is take that TORCH junk plug and throw it in the trash and replace it with an NGK and check the gap. In my experience I have seen bad spark plugs cause all sorts of headaches. If the bike acts the same, I would take the timing mark cover off and roll that crank around until you line up and center the "F" in the window or with the pointer. Then I would pop that valve cover off and make sure BOTH valves are closed and there is a slight amount of play in the rocker arms. In other words the rocker isn't putting any pressure on the valve. That should give you some clue as if the timing is right. When you roll on the throttle when starting the engine is trying to ignite the mix you just let into the engine, but it sure seems to me like it is trying to ignite it at the wrong time thus stalling the starter.

[NzBrakelathes]

Did you buy my kit? For first tune and basic mods etc?
Look in my eBay store

Swap plugs mate see if you can move the fault

Found this too and thought interesting

[Megadan]

Originally Posted by Johnny_Sardine

If I got it to putter, and just very barely gave it the smallest amount of throttle, a couple times it started to rev. Then I was able to open it up. It revved and wasn't even, it backfired. The carb will also shoot gas out the intake when the choke is on.

This sounds to me like either the cam timing is off, or your valve lash was set at the wrong TDC. There are two TDC points, one at compression and one at exhaust. If you set the valve lash on the exhaust stroke, where both valves are actually being activated by the cam a little bit, then your valve lash will be enormously out of spec. The easiest way to know is to roll the motor over, and watch the rocker for the intake valve. Once it actuates, the next T mark on the flywheel will be TDC for the compression stroke. It wouldn't hurt to double check and make sure you have this right.

As far as having the throttle open and the starter having a harder time, you are trying to compress a larger volume of air than you would with the throttle closed. You can hear this on any healthy bike when you try to start it and open the throttle, it takes more power to compress a larger volume at the same ratio.


I was also having the same thought as paulsstag. Swapping carbs with the same result tells me it isn't the carbs. However, the intake to the head can be the culprit via a vacuum leak. The O ring that seals the intake to the head may be pinched or missing, or the flange was bolted down too heavily and warped the flange (it's soft aluminum), or the rubber may have a rip in it somewhere.

Another possibility. While the battery may say it is charged, it is possible that it can't supply the proper amps to run both the starter and the ignition. Having spark doesn't always mean it has good spark. Try swapping the Hawk battery over, or hooking a set of jumpers up to a car battery (without the car running!) and see what happens. My last battery was causing very similar symptoms, which is why I bring it up.

[JerryHawk250]

Originally Posted by Megadan

I was also having the same thought as paulsstag. Swapping carbs with the same result tells me it isn't the carbs. However, the intake to the head can be the culprit via a vacuum leak. The O ring that seals the intake to the head may be pinched or missing, or the flange was bolted down too heavily and warped the flange (it's soft aluminum), or the rubber may have a rip in it somewhere.

^^^This is what I was thinking. ^^^ Air leak

[Johnny_Sardine]

Alright well I rechecked the valves finding compression like you told me and I must have had it wrong cause the exhaust valve was way too loose. Got them both to .002 and closed it back. Threw the mikuni back on, changed the plug to an ngk. Kind of doing the same thing. Checked the carb to head gasket thing and it looks fine.

Looking around for more loose stuff or anything that can cause an air leak and found a dodgy looking situation where the exhaust bolts to the engine but maybe that's normal? not all the way seated but....


So I can get it to putter still and I got it to fire up twice but shit is smoking and it's backfiring and the exhaust is heating way up... It will not start with the choke on at all so is it running super rich??? Confused. Here's a video, first part is me trying to start it and puttering, second part is the smoking mess it is when it's fired up. First time it starts it rattles cause of all the shit I have on top of it.




What would be the best way for me to check if the timing is 180 degrees off?

Thanks y'all. I really appreciate it.

[JerryHawk250]

Stopped up Cat???? Man the cat heated up quick. Disconnect the header but don't rev it up or anything just to see if it will idle.

[Johnny_Sardine]

I know... it ran for like 20 seconds...