k75 starts bu wont accelerate????

[k75chip]

Got this '87 k75 back end of last year(well neglected sort)for a cafe racer project.
Anyhow light stripdown of engine( just a nosey around really) and full frame and bike tear down to makeall shiny and new .
All back together now and looking good,but wwon't run!
New injectors,new fuel filter,new hoses( fuel and vacuum),fuel pump tested and running at 35psi new plugs .
Starts on the button every time but won't rev( dies as soon as throttle opens.Smells really rich fuel wise.
So replaced Maf sensor and ecu....exactly the same as before,so put old plugs back in...still the same
New coolant temp sensor...still same??????
Checked and cleaned all earth points .
One question tho the fan was knackered so as it stand it doesn't have one,will this have any effect on anything?
Please help me as I live in england and the summer only lasts a couple of weeks and would like to get a run out before the winter gets here.
Any clues ?

[Scott_]

The cooling fan shouldn't have any effect of the fuel/air mixture issue. There are aftermarket options for replacing the fan. Either just the motor or the entire assy. You can search here on this site.

You didn't mention anything about the tps switch, out of adjustment?

[k75chip]

The tips on these older models is a simple off idle or full throttle type and basically just prevent back firing on throttle closure so the bike will run with or without the tips connected

[Motorhobo]

So you're getting fuel but no air to burn it with? Sounds like no air is moving at all. Did you put the crankcase breather hose back on? Long shot but can't hurt to ask.

[rbm]

Have you checked the hall effect sensor assembly?  Might be one of the sensors is knackered.  There is  available a simple test circuit using a LED to see if the unit is functioning. 

[vintagemilano]

Maybe the fuel pressure and return lines are backwards at the tank.

[rbm]

Maybe the fuel pressure and return lines are backwards at the tank.

Then it wouldn't start at all.  DAMHIK

[k75chip]

Thanks for replies so far,the bike does seem starved of oxygen but all breathers are in place and in tip top shape,as for the hall effect sensors I understand that the bike would either not start at all or run fine for a while and then cut out ,but neither of these symptoms apply.
Keep posting me anything that springs to mind as you never know!?
Thanks again

[wmax351]

Try unplugging the TPS, could be sending the "Throttle Closed" reading, which would keep it from revving above 2000 or so.

[k75chip]

Tps been disconnected.........same old ....

[Motorhobo]

Grasping at straws here but what do the plugs look like after it dies on throttle up? All three Wet with unburnt fuel? Maybe it's not air-starved but rather flooding. What about those new injectors...sure they're giving the correct flow rate? What kind did your replace them with? Did you Also replace all the injector o-rings? They're supposed to be replaced every time you remove the injectors, at least the lower ones.

More silly questions -- after it dies on throttle-up does it start right up again at idle or does it struggle? Have you tried setting the idle screw higher and bypassing the throttle cable? Will it start with the 'choke' lever on highest setting? I guess I'm thinking maybe the starting point for diagnosis should be the mechanical link between the throttle grip and the the throttle control lever.

Then I'd want to determine whether the problem is not enough air or too much fuel. Maybe someone else can help with a way to figure that out...

I'm also wondering whether the fuel pressure regulator could be the culprit...not sure how to test that but it might be in the Lieberry. Any help?

[k75chip]

Plugs are sooted up(each one the same)when removed and yep the bike fires straight back up but only on idle although occasionally if the throttle is held wide open on starting it will rev but very erratically then die after a minute or two.
Gonna pull the injectors tomorrow and check the flows.
Will post any results then.
Cheers all

[K75RT Keith]

Are they stock injectors or a 4 pintle semi equivalent?  A couple of the "upgrade" injectors have different impedance values that can run way rich on a K75

[k75chip]

Injectors are Bosch 0280150716 slightly lower impedance15.9 as oppose to 16.2 on standard Bosch injectors but flow rates almost identical

[k75chip]

Just dawned on me ,the injectors I have fitted have almost identical impedance and flow rates,but I'm not sure at what fuel pressures they run at( standard injectors are around 2.5 bar but don't know the ratings of the newer ones?)again standard injectors are bocsh 0280150210 new ones are0280150716.
Anybody help?

[rbm]

Bosch Injector Data spreadsheet

I think the "6" on the end of your second Bosch part number is not right.  I was able to find an injector with p/n 028015071 in that document.

[k75chip]

Found a Bosch injector cross reference site with all types inc flow rates,impedance and pressures etc and the only difference between the two types210 over 716 is that the latter specs are done on a 3 bar pressure and the former on a 2.5 bar pressure.
 Could this be the problem/solution.
Looking for a definitive answer here because it will involve a large expenditure if I need another set of injectors.

[rbm]

I don't know if this helps or not.  My K75 is fitted with standard K1100 injectors instead of the lower flow rated K75 injectors.  These are Bosch P/N 0280150710 and are rated for 103 g/m at 2.7 bar.  these injectors work perfectly in my bike and even with a higher flow rate, I'm getting better gas milage apparently.

[Motorhobo]

Not sure if you've gotten this sorted yet but here are some threads relating to throttle issues --

http://www.motobrick.com/index.php?topic=5443.msg33937#msg33937

http://www.motobrick.com/index.php?topic=5443.msg33937#msg33937

Before you go replacing or pulling those injectors again -- assuming you've confirmed that the parts # s are correct and the injectors are proper for your bike, you might want to invest in the HF fuel pressure gauge referenced in the link above. I did some searching through Workshop posts -- didn't find any where any throttle above idle caused stalling as in your case. The second thread above explains how the FPR works -- by that description a failure could cause the symptoms you have.

It'd be a drag if you went thru all the hassle of dealing with injectors only to find out fuel pressure was the issue...

[k75chip]

Hello again,I have gone through the wiring/connectors with a fine tooth comb all seems good and have a fuel pressure gauge permanently mounted(35 psi all the way).
Think I'm gonna get another set of injectors and at least eliminate that as the problem.
Will be in touch soon as,cheers

[mjydrafter]

Don't know where you guys are finding you injector info but Witch Hunter has a lot of good info.

http://www.witchhunter.com/injectordata1.php

They don't cross what vehicles they are on, so that requires a bit more searching if you find an uncommon injector that you like.  But they have the pressure, flow rate, and resistance of most of the Bosch injectors.

 

[k75chip]

There's a site out there by Stan Weiss(srweiss/tablefic.htm#bosch)plenty of injector info on there