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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: Lbxpdx on March 27, 2024, 06:05:11 PM
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I’ve been trying to hunt down a small issue since I bought this bike, 1993 K75rt with 108k miles, this last summer. I’ve noticed a small miss when holding the throttle steady, though everything is fine at idle or accelerating. It kinda feels like a gust of wind.
Cleaned tank
New odyssey battery
Changed fuel filter
New air filter
Changed oill/filter and coolant
D7ea plugs with NGK wires
New upper boots for the TB
Synced TB’s with twinmax
professionally cleaned injectors
Cleaned ignition switch and kill switch
Tested temp switch in water and everything is in spec
Valves are spot on
Fuel pressure is good
Alternator brushes are long
Grounds have been cleaned
DeOxit on most of not all connections
New header crush gaskets (header to exhaust have not been checked)
Yesterday, around 45 miles from home, I decided to disconnect the TPS, and found it ran great. It felt like it was breathing better, much easier to get to 8k and it felt like it pulled better in 5th.
The missing is still present, though it is not as bad as it was when I first bought the bike.
My question is if the bike runs better without the TPS connected, does that mean I have the TPS incorrectly set? It click right as the accelerator is pulled.
I know my idle should be 1000, but it seems I’m around 1200.
I haven’t checked the Air mass meter adjuster under the plug.
I have run multiple bottles of Techron and one bottle of sea foam. I generally only use Chevron or non ethanol fuel.
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K75s seem to benefit from having the vacuum ports interconnected. I was initially skeptical about this mod but now I'm totally sold on it. I don't believe you have to fit a system with a reservoir, Tees and hose works just fine. Bruce is happy with his conversion and I believe Dan is still running his, even though the benefits aren't as great on the K100. https://www.bing.com/ck/a?!&&p=e76c45c31816b70cJmltdHM9MTcxMTQ5NzYwMCZpZ3VpZD0xOThkZGI2ZS03OTYxLTZjOTYtMGY2MS1jOTE4Nzg4ZDZkZDUmaW5zaWQ9NTE5NQ&ptn=3&ver=2&hsh=3&fclid=198ddb6e-7961-6c96-0f61-c918788d6dd5&psq=K100+forum+Vacuum+Modification&u=a1aHR0cHM6Ly93d3cuazEwMC1mb3J1bS5jb20vdDE1MjEyLXZhY3V1bS1tb2RpZmljYXRpb24&ntb=1
Regards Martin.
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Your link is funky
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It's still funky but connects. :idunno:
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Can you post a pic of your vacuum block?
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I just used 2x5mm Tees and 4mm vacuum line. The vacuum line required lubrication to get it onto the Tees I don't believe a vacuum block is needed. The 2 Tees in a Champion Pack were $8.00 Au and the 4mm vacuum line was $8.00 a metre.
Regards Martin.
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I just used 2x5mm Tees and 4mm vacuum line. The vacuum line required lubrication to get it onto the Tees I don't believe a vacuum block is needed. The 2 Tees in a Champion Pack were $8.00 Au and the 4mm vacuum line was $8.00 a metre.
Regards Martin.
That is what I did. Cost less than $10.
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So what do you reckon Gryph has it improved your slow speed and your throttle response?
Regards Martin.
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It seemed to smooth out low speed running a little, it wasn't so jerky off idle in slow speed situations. Sold the bike shortly after doing the modification so no long term perceptions.
The main thing was that the idle was a little smoother, about what I could get with a good throttle body balance. It could be the response of the pressure regulator to changes in throttle was a bit better because there were three vacuum ports pulling on the regulator diaphragm instead of one. I suspected that better regulator response might help the backfiring on overrun, but never got a chance to test it.
It certainly didn't hurt anything.
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Slightly off OP topic, but I've connected all 4 of my vac ports together for purpose of vac source for cruise control use. No extra capacity chamber, but do have a check valve in line before controller.