Inlet port full of fuel?!

[VFR400+]

Got a problem in that the bike doesnt seem to be running right. Got a twin stack exhaust and the upper one that links to the front cylinders runs hotter than the lower one that runs from the rears. Also if I stick my hand over the lower end cap it doesnt change the idle. Do the same on the top and it drops off as expected. Tightened up the headers on the rear as they were leaking slightly but didnt help much

After doing some reading thought it could be possible that one of the rears wasnt sparking. Tested the resistance of the ignition coils and the rear one measure 3.8 the front 3.6. Was gonna test for spark although the machinist has one of the sparks to match the thread for the compression tester adapter.

One of the threads I read mentioned the pilot circuit could be blocked. Thought this could be the issue as if reved the pressure increased. So removed the carbs to give an other clean. On doing so I noticed one of the rear inlet ports was full of fuel!! I used a syringe to draw it out, there was none in the cylinder. Had the carbs on and off a number of times and its not happened before. Have replaced the bowl gasket rings, checked the float heights all within 6.5-7mm.

Blasted plenty of carb cleaner through all the jets and think its fair to say they are clear. Gonna have to wait to get my spark plug back to test anything.

Any suggestions would be greatly recieved!

[265chemic]

When I first bought mine - (not running) this happened during course of getting it back up to scratch.

The problem will be your needle and seat arrangement - the needles arent seating properly (either cos theres something on the needle/seat that is stopping it doing so) or in my case, the float hinges are a bit shithouse and they arent closing the needle and seat valve properly. Best to take the float and needle out and inspect to make sure they are clean and swing smoothly.

The second issue will be your fuel tap - the vaccum diapraghm setup within is designed to stop this happening in the event your needle and seats dont close properly. Have you done the fuel tap mod? (test by checking if the tap flows fuel when engine is off) - its possible it drips just enough to result in the above.

The only real negative effect (aside from losing fuel and possibly hard starting) is that your sump could end up with fuel in it, thinning out the oil and potentially causing damage to bearing surfaces.

If you'd like any more info on any of the above, just say.

Pete

[Neosophist]

If you hold the throttle at 5500rpm for 30 seconds do all the pipes get warm?

If they do then this points to your idle circuit being at fault.

Either it's dirty and gummed up (common) and you haven't cleaned them out properly.. the idle circuit has lots of small passageways including 3 tiny holes that lead to the butterfly that need to be clean.

You haven't mentioned pilot screw settings either are these all the same.

Or if the carbs are ok then the balance must be off by quite a bit, check the valve clearances and balance the carbs.

[VFR400+]

Thanks for the advice guys, as soon as I get the spark back I will try holding the revs at 5500 and see if the pipe all get hot. The pilot screws were all 2.5 turns out (standard airbox with full Jha system) I did have 33bhp restrictors fitted. I took them out when refitting the carbs as they seem to seat better without them.

I balanced the carbs with the drill bit method previously and checked it again yesterday and they were slightly out so did it again using a 0.015 feeler gauge which felt much more accurate.

Have ordered some new spark plugs as well just so I can swap them around and try that.

Hopefully its just a carb or spark issue as don't want to drop the engine again!!

[Lane]

A bad engine doesn't cause excess fuel to enter it's ports..... poorly set up carbs do.

[VFR400+]

I have checked over the carbs and fitted new plugs and it now runs on all four cylinders one of the plugs was quite wet. Im worried that if the carbs were flooding the cylinders then im gonna have fuel in the oil. I had a good sniff of it and it does smell of fuel although its quite hard to tell as the oil smells almost fruity by itself. Im gonna drain the oil and try again...pity as the oil is brand new and the bike hasnt done a mile on it yet!

@ 265chemic I havent done the HRC mod although Im gonna check the tap doesnt leak.

Ive removed the carbs again and Im gonna tripple check the floats as Im now parnoid about hydrolocking the engine or the bottom end failing due to petrol getting in to the slump over time.

Lastly whats the chances if there is petrol in the oil its now destroyed the new clutch I put in?

[Lane]

Clutch will be fine, just change the oil.

Use some budget shit if you are still not confident that your set up is 100%, then replace with better stuff once your sorted.

[265chemic]

It becomes a question of how much fuel in the oil too - if there isnt much it will evapourate once the bike is heated to temp. just be aware of how much oil is in there (take note of dipstick level) and if it is overly runny compared to normal.

[VFR400+]

Theres plenty in there! Was just under the max mark when filled and how its about 10mm above and Ive lost a fair amount of fuel! Having recently rebuild alot of the engine think I will just change the oil.

Gonna try to order a fuel tap kit today as it needs to be on the road this week!