TBR7 Won't start

[paulsstag]

Originally Posted by Johnny_Sardine

Alright... seems like maybe I'm getting closer, but still no luck.

I've swapped a lot of parts off the hawk by now and nothing is working on the TBR7. I did the valve clearances and they were super tight. now .002 for both. Still has the stock hawk carb. When I go to start it, it would putter for a second then die. It would not even try when the throttle was open or the choke was even half on or the air box was connected.

When I undid the air box hose, left the throttle alone, and no choke, it would putter. For a couple seconds max. Every time I give it gas, the starter just seizes... I have no idea what would be causing this because as far as I can tell there's not even an electrical component to the throttle. Why would it interfere with the starter??

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.

So the mikuni that I rejetted? Threw that on the hawk and it runs like a champ. Idles and pulls. I have no idea what is going on with the TBR7...

How would I go about testing something like the killswitch or the ignition coil or...? At this point, the freaking bike just won't run, while the hawk hit the ground running. I'm at a loss.

Thanks for the advice, been listening to it all.

Sounds like a serious air leak to me. If it trys to start and sputter its not electrical. Check the rubber connector from the carb to the cylinder head , it may not be on straight or the o ring is missing . you can also spray wd40 around that area while your cranking the engine. If it runs while spraying the wd40 then its leaking ( sucking air ) in that area.

Let us know

[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...

[Johnny_Sardine]

So disconnect the exhaust?

[JerryHawk250]

Originally Posted by Johnny_Sardine

So disconnect the exhaust?

Yes, just to make sure it runs. But don't go revving it up. You just want to check if there is a restriction in the exhaust. It may even have something in the exhaust blocking it.

[Johnny_Sardine]

Ok so now it will sputter up for 2-4 seconds... not evenly, then die. ONLY will it do this when I have it unchoked, no throttle and the airbox unhooked from the carb. Basically the same behavior, just sputtering more consistently and a little longer.

The fact that the bike is starved for air, backfiring and bogged down says to me that it's either getting too much gas... or it's not able to burn it properly... that send me to the timing? I feel like a vacuum leak would be the opposite problem... and I did check the airbox to make sure it was normal... seems alright.

Would it be a simple matter to fix the timing (if it is wrong) or should I get in touch with Q9 about a replacement or refund? Because the hawk is running great so something is up.

[Megadan]

I would get in contact with Q9 about the issue. They will likely want you to do some trouble shooting, and even if it is stuff you have already tried/done, just humor them. This would definitely be a warranty issue in my book.

The fact that the catalyst got that hot that quickly is disturbing. Did it do that when you tried the carb from the Hawk?

[Johnny_Sardine]

Cool, Dan. Thanks for the input guys. I'll give them a call first thing tomorrow.

Yeah it heated up like that every time we managed to get it to run. With both carbs. It must just be spitting out flaming gas or some shit.

I'll keep you posted on the situation.

[Megadan]

Originally Posted by Johnny_Sardine

Cool, Dan. Thanks for the input guys. I'll give them a call first thing tomorrow.

Yeah it heated up like that every time we managed to get it to run. With both carbs. It must just be spitting out flaming gas or some shit.

I'll keep you posted on the situation.

I wont deny that possibility, but I would almost wager more that Jerry's suspicion is correct and the catalyst might be bad. A severe clog right there would explain a lot of your symptoms, and why it gets to glowing red hot so quickly.

I would be tempted to swap the exhaust systems around just to see what happens.

[Johnny_Sardine]

So even though the bike is acting the same with the exhaust disconnected?

[JerryHawk250]

Did you check the plug again to make sure it didn't get fouled up?

[Johnny_Sardine]

yeah it's had 3 plugs in it at this point. Brand new NGK this morning.