MOTOBRICK.COM

TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: Steviescumbag on July 24, 2020, 09:38:19 PM

Title: What could be the reason for my 92 K75 rt feeling jumpy
Post by: Steviescumbag on July 24, 2020, 09:38:19 PM
My brick turns on fine and idles fine. But when I ride, the bike feels jumpy. As if it is losing gas, like it’s about to die on me. It also lags when I give it gas. the engine sounds fine and there are no leaks. I just changed the Crank Case Breather vent tube so I don’t think it’s that.

Could it possible be some carburetor issue or fuel line issue? How would I know if it is?

It just started doing this, this week.
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: Laitch on July 24, 2020, 09:56:24 PM
Welcome!

How long have you had this moto? Have you looked inside the fuel tank? Common reasons for fuel starvation are faulty fuel filters, loose fuel tank hose connections and deteriorating fuel tank hoses. Remove the fuel cap assembly, remove the fuel, remove the fuel filter and try to blow through it in the direction of fuel flow indicated by an arrow on it. Inspect the hoses for cracks and loose connections.

Your moto doesn't have carburetors; it has a fuel injection system. Please post a photo of your moto! It can help others to see what you're riding.
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: Steviescumbag on July 24, 2020, 10:41:02 PM
Appreciate the reply my man!

Yes I realized after this post that it uses
Injectors lol. Derp.

Do you feel it can be the fuel injectors?

Also I might have dropped the bike not saying I did lol. Not hard! Just laid it down but it was tipping and I couldn’t hold. but got it up ASAP. :(

I have had this bike for 4 months now. It is a 92 k75rt. It was well taken care of by an old gentleman whom I bought it off. Has 57K kms.

Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: Laitch on July 24, 2020, 10:56:28 PM
Do you feel it can be the fuel injectors? 
I've already shared my feelings.  :laughing4-giggles: It's somebody else's turn.
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: daveson on July 25, 2020, 01:40:05 AM
I feel that to be initiated into the brick fraternity, you need to drop it while stationary and on the right hand side. Hopefully you dropped it on the right hand side then you wont have to do it again. Or was it the left?

Sometimes it's something very simple, like a spark plug lead not fully pushed onto the spark plug, or other end, especially considering it happens under load. 
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: blackie1 on July 25, 2020, 03:08:09 AM
so in the four months of ownership how did it run.

if it used to run great... did you meddle with or change anything just prior to it not running great.

 my initial guess would be that it is sucking in air from a cracked rubber component once you open the throttle
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: The Mighty Gryphon on July 25, 2020, 08:18:18 AM
Do you have NGK spark plugs in it?  The "proper" NGK D7EA plug has the wrong terminal for the bike's plug wires.  They need a "terminal nut" to make the correct connection with the connector on the plug wire.

When the plugs are new or under small throttle openings the plugs fire easily so the bad connection isn't a big deal, but when you open the throttle the cylinder pressures increase and the plugs need a better connection to fire consistantly, especially after they get some deposits on the electrodes.
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: Scott_ on July 25, 2020, 09:37:36 AM
I'd be curious what else was removed from this moto, besides the fairings..... If it's supposed to be an RT, someone has done some modifications on it.
As Laitch has suggested, I'd be checking the fuel filter 1st, then I'd suggest getting some techron FI cleaner and run some of that thru a couple of tankfuls of gas.
After you do that, if it's still acting up, we can go deeper.
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: Steviescumbag on July 25, 2020, 09:51:25 PM
Thanks for the feedback boys. I’ll start with the basic checks and I’ll come back to update the squad. Thank you

Nothing other than the fairings was removed from the RT. (Headlight and blinkers were included in that removal! )
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: Steviescumbag on July 25, 2020, 09:54:11 PM
The moto was running greet since I I bought it. No mechanicals were changed or tampered with.
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: Steviescumbag on July 28, 2020, 07:40:39 PM
There seems to be a leak here. Any feee back on this piece?

Gunk buildup
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: Laitch on July 28, 2020, 09:19:12 PM
There seems to be a leak here. Any feee back on this piece?
Leaking components controlling air intake change the fuel mixture. Leaking rubber throttle body manifolds and bushings should be replaced. A problem with neglected old motos is deteriorating rubber components—fuel lines, intake manifolds, the crankcase z-hose, the throttle body vacuum caps, the fuel pressure regulator vacuum hose. There's plenty of information in posts here on diagnosis and treatment.

Here's a link to identify the parts (https://shop.maxbmw.com/fiche/DiagramsMain.aspx?vid=51743&rnd=07242017) and OEM part replacement costs .
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: stokester on July 30, 2020, 06:55:30 PM
There seems to be a leak here. Any feee back on this piece?

Gunk buildup
Did you spray some brake-kleen or other volatile cleaner to confirm that?
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: Steviescumbag on August 15, 2020, 07:01:42 PM
I figured out the issue. I changed my fuel filter with a Napa Gold 3032. The bike is up and running like a dream. I noticed it as soon as I turned it bike on. The idle sounded cleaner and meaner. The ride is even better than before I ran into the problem.

Thanks friends 👍🏼
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: stokester on August 15, 2020, 07:30:34 PM
I figured out the issue. I changed my fuel filter with a Napa Gold 3032. The bike is up and running like a dream. I noticed it as soon as I turned it bike on. The idle sounded cleaner and meaner. The ride is even better than before I ran into the problem.

Thanks friends
OK
Was it a faulty/clogged filter or a bad hose/connection? :popcorm
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: Steviescumbag on August 15, 2020, 07:39:06 PM
It was clogged. I could of cleaned it but for the price of a fuel filter there is no point.
Title: Re: What could be the reason for my 92 K75 rt feeling jumpy
Post by: Billk on August 21, 2020, 02:20:15 PM
I never do too many things at a time and I check by riding the bike for a while. Always check the last thing you’ve done even if the last thing seems meaningless or impossible to cause the problem your confronted with.