TBR7 fuel problem

Slug · 09-15-2024, 12:11 AM

So, over the last month or so I've had some weird power loss issues which I believe I've fully narrowed it down to being fuel delivery but now I'm encountering another problem.

I'll go into some detail here about what happened last week.

Finally got a completely separate problem solved which was a new axle for my swingarm and was excited to go ride that day. Rode it around the house a few times to make sure everything was good with chain, swingarm, and wheel being tight and not moving.

Now where this new fuel issue comes into play is I was out and the bike was constantly losing power like when you're running out of gas. Had a hell of a walk back home that day because the bike completely died and wouldn't start back up.

tl;dr fuel not getting from carb to engine. Took the carb apart and completely replaced my jets, the bike occasionally started but only at like 8k RPM and would immediately die if choke was off.

Where do I go from this point? I can get the bike to run if I pour fuel directly into the spark plug hole, but it still runs at 8k RPMs before dying again due to no fuel getting from carb.

Edit: With such high RPM I'm thinking there's a vacuum leak somewhere. Oh and I'm also getting backfire from the air intake when it's starting.

XLsior · 09-15-2024, 12:45 AM

carb float needle valve perhaps...

bad petcock/blocked tank filter?

tank breather?

Slug · 09-15-2024, 12:55 AM

Quote:

Originally Posted by XLsior

carb float needle valve perhaps...

bad petcock/blocked tank filter?

tank breather?

I'll check the float again to make sure it isn't stuck.

I put new fuel lines and filter on earlier this year and they don't look clogged up.
I'll have to drain the tank and pull the petcock to see if that's clogged.

TBR7 cap doesn't have a breather hose like the Hawk.

superjocko · 09-16-2024, 03:46 PM

Does it have an evaporative emissions canister? If so, check that the lines to it haven't been inadvertently switched. My CSC TT250 came that way straight from the dealer and would run out of fuel after a mile or so of riding. After popping the fuel cap to allow the tank to vent it would run fine for a bit until it developed a vacuum in the tank again. I then ran it with cap not fully seated and it was fine. After a bit of sleuthing to determine how the tank was vented I discovered the lines to the canister were switched. I contacted CSC to give them the heads-up and they said they'd had that happen before and would stay on top of it better going forward.

Slug · 09-17-2024, 01:54 AM

Was able to get the problem solved yesterday.

It was the gasket between the intake manifold and engine that was completely knackered causing a massive vacuum leak.

Engine is running a bit hot now so I'll have to adjust the jetting and possibly get back into the valves as well.

09-15-2024, 12:11 AM	#1
Slug Join Date: Sep 2019 Posts: 69	TBR7 fuel problem So, over the last month or so I've had some weird power loss issues which I believe I've fully narrowed it down to being fuel delivery but now I'm encountering another problem. I'll go into some detail here about what happened last week. Finally got a completely separate problem solved which was a new axle for my swingarm and was excited to go ride that day. Rode it around the house a few times to make sure everything was good with chain, swingarm, and wheel being tight and not moving. Now where this new fuel issue comes into play is I was out and the bike was constantly losing power like when you're running out of gas. Had a hell of a walk back home that day because the bike completely died and wouldn't start back up. tl;dr fuel not getting from carb to engine. Took the carb apart and completely replaced my jets, the bike occasionally started but only at like 8k RPM and would immediately die if choke was off. Where do I go from this point? I can get the bike to run if I pour fuel directly into the spark plug hole, but it still runs at 8k RPMs before dying again due to no fuel getting from carb. Edit: With such high RPM I'm thinking there's a vacuum leak somewhere. Oh and I'm also getting backfire from the air intake when it's starting.
	0

09-16-2024, 03:46 PM	#4
superjocko Join Date: Aug 2022 Location: Lincoln CA Posts: 134	Does it have an evaporative emissions canister? If so, check that the lines to it haven't been inadvertently switched. My CSC TT250 came that way straight from the dealer and would run out of fuel after a mile or so of riding. After popping the fuel cap to allow the tank to vent it would run fine for a bit until it developed a vacuum in the tank again. I then ran it with cap not fully seated and it was fine. After a bit of sleuthing to determine how the tank was vented I discovered the lines to the canister were switched. I contacted CSC to give them the heads-up and they said they'd had that happen before and would stay on top of it better going forward. __________________ -2024 CSC TT250, stage 3 motocult kit, Nibbi PE28FL with custom-made cable controlled choke, modified stock muffler (larger diameter tailpipe), custom oil cooler installation with relocated stock evaporative emissions canister, oversized stainless steel footpegs, IMS folding tip shifter, a few little blingy bolts and bits. More personal preference mods to come.
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09-15-2024, 12:45 AM	#2
XLsior Join Date: Aug 2020 Location: Australia Posts: 1,444	carb float needle valve perhaps... bad petcock/blocked tank filter? tank breather?
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09-17-2024, 01:54 AM	#5
Slug Join Date: Sep 2019 Posts: 69	Was able to get the problem solved yesterday. It was the gasket between the intake manifold and engine that was completely knackered causing a massive vacuum leak. Engine is running a bit hot now so I'll have to adjust the jetting and possibly get back into the valves as well.
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