#6

[speedpro]

The cylinder head I used was a 2KR head. The 3LN head I have had dropped a valve in #3 so it was easier to use the 2KR head. I have a stack of unused springs to measure and pulled one out of the 3LN head for comparison. The 2KR springs are all the same length +- not much. The 3LN spring is .5mm longer. However the 3LN spring is slightly thinner wire. All springs are progressively wound, 2 steps in the winding anyway.

Thinking about it the valves must be floating. There is a horrible noise which suggests this is the case as well as the problem. If it was a simple problem with VE it would be vastly different with the turbo and it isn't. So I need new springs, or as Grumph I need to shim the springs up. Should be able to do it without removing the head.

[Grumph]

So I need new springs, or as Grumph I need to shim the springs up. Should be able to do it without removing the head.

I'd like to be there and watch that.....Air pressure ? large magnifying glass.....

Some time back, I built a new engine for one of Kickaha's then sponsors. A turbo'd 1400 Kawasaki in a Radical sports car. Anyway, the old one had a big exhaust cam in it - and there were signs the ex valves had tagged the pistons despite heaps of valve-piston clearance. Std springs too. Anyway talking to Kev Ban at kelford about it, he quoted problems with surge in the headers of turbo'd Subarus which gave such high pressure spikes they were holding valves open, tagging them and blowing the lot apart. I talked to a guy oop North who was the turbo Radical guru who simply said "put in a std cam on about 110 lobe center - it'll fix it. It apparently did as there have been no reports of trouble.
I can't help wondering about wave activity in a 180 deg twin header....

[husaberg]

looking at the basic spec there was a model between the 2kr and the 3ln
the i never heard of
it looks like a 3ln with 3kr frame and single disc this version and the first years 3ln had the hotest specs and highest redline 19500rpm
frame numbers for the highest reving ones
Model Designation Frame Numbers

3HX1 2KR-164101 -

3HX2 2KR-210101 -

3HX3 2KR-214101


or 1989

3LN1 3LN-218101 - 279000



The 1990 on one were detuned not sure if electronic or other ways.

Here is the 3ln specs for the post 1990 3LN


Also we have
2KRs are 26mm BDS26
3LNs are 28mm BDST28

1. 2KR
2. EXUP (engines before 3LN) 3HX but still with 2kr style frame and single disc
3. 3LN early, with oil filter in sump plate
4. 3LN later, with spin on canister oil filter


The connecting rods on the 3LN1 are longer than previous (82mm vs. 80mm), the cams are different in terms of duration (difficult to measure) and the pistons are lighter and have gudgeon pins offset from central axis and I assume a different deck height to account for the longer rod.

Valve for YAMAHA FZR250 3LN 1SET
Stem diameter: 3.5mm;
Length: 77.5mm;
The top of the intake port: 19mm;
Top of the exhaust port: 15.5mm.


Valve for YAMAHA FZR250 1HX 1SET
Stem diameter: 4.0mm;
Length: 77.5mm;
The top of the intake port: 18mm;
Top of the exhaust port: 16.5mm.

[F5 Dave]

Jesus-mother-arse-fucking-Christ this all seems overly complex. Isn't there some KISS solution to all this palava?

[speedpro]

Probably.

I could build a 30hp 2-stroke. There is a certain complexity to that though, as you well know.

Running it in the garage last night it just sounds sooo good. The throttle response is instant and the date logging shows it will blip from 2000rpm to 6-8000rpm in .2s. I'm pretty sure it is faster picking up with a few revs on. The 180' twins sound great. One thing I finally got round to checking was the current draw from the battery. At about 2000rpm, without the Lambda on, it was drawing 2+amps. Surprisingly it rose as I brought the revs up and exceeded 3A at 6000rpm. It will be interesting to see what it is pulling at 15000. With dwell control on the coils I knew it would increase but didn't expect it to increase that much. Might need to seriously look at putting the rotor back on and using the standard teeth arrangement on the rotor just so it can generate some electricity. Having a bit of inertia on the crank might also stop some of the chatter from the gearbox.

[Grumph]

On track you'll never notice any gearbox chatter.

That's a bloody high current draw. My 500 kawa twin running total loss battery power draws 1.6 amps right across the rev range - which is a pretty normal draw for most basic TCI ignitions in my experience. Even a Dyna on a four draws about that.

[speedpro]

Had a chat with Kev about what could be done about measuring the valve spring tension. I've decided I want to measure the spring tension at near zero lift and maybe a couple of other points, say 1,2,3mm. We've come up with an idea for a block that bolts to the head using the cam cap bolts and puts pressure on the valves by turning a screw. Between the screw and the valve will be a small hydraulic chamber which will be free to move in the mounting block with a gauge connected. One end of the chamber will have a piston which is free to move and will be pressing down on the valve. The fluid pressure will therefore be proportional to spring tension. A simple bit of maths will provide the actual pressure on the spring at various lifts.
I was hoping to use a tool that was made when I had the head on the bike prepared for use. It fits in the valve guides and the valve seat cutters fit on the larger diameter portion of the shaft. The bit of shaft that goes in the guide is 4mm diameter. It wouldn't go in the guides of the spare head. Turns out the newer valve stems are only 3.5mm diameter. It's going to be a bit of fun on the mill clocking it all up to get the angle but after that it's pretty straight forward.

[husaberg]

Had a chat with Kev about what could be done about measuring the valve spring tension. I've decided I want to measure the spring tension at near zero lift and maybe a couple of other points, say 1,2,3mm. We've come up with an idea for a block that bolts to the head using the cam cap bolts and puts pressure on the valves by turning a screw. Between the screw and the valve will be a small hydraulic chamber which will be free to move in the mounting block with a gauge connected. One end of the chamber will have a piston which is free to move and will be pressing down on the valve. The fluid pressure will therefore be proportional to spring tension. A simple bit of maths will provide the actual pressure on the spring at various lifts.
I was hoping to use a tool that was made when I had the head on the bike prepared for use. It fits in the valve guides and the valve seat cutters fit on the larger diameter portion of the shaft. The bit of shaft that goes in the guide is 4mm diameter. It wouldn't go in the guides of the spare head. Turns out the newer valve stems are only 3.5mm diameter. It's going to be a bit of fun on the mill clocking it all up to get the angle but after that it's pretty straight forward.

The earlier head might be better for the Turbo version with its bigger ex valves?

[speedpro]

Valves are the same size, just the stems changed. The spring retainers are different as well and the buckets.

[Grumph]

That's a lot of work to measure the spring pressures. If you have spares, it's grab a retainer, measure the installed height on a spare head - and off to a cam grinder/speed shop who have a spring measuring tool....
I've done just that so often at Kelford's, they barely look up when I come in.

[speedpro]

I don't know the installed height of the springs in the head on the motor. I'll be able to compare the seat pressure to the standard seat pressure of the 3LN head and also what Husa has provided above. It should be pretty simple to come up with a spring shim that should make it work. If the engine in the bike has a lower seat pressure than the 3LN head I'll be able to screw it down until it is equal and that will be exactly the height I will need to shim the spring.

I weighed a few bits tonight and it was very interesting. 2KR/3LN in grams - ex valve 10/10, spring retainer 5/4, tappet 12/8. All together 28/21. Unfortunately the spring retainers can't be swapped as the valve & collett combination won't fit. There is a useful reduction in weight going to the newer tappets of 4-5g or about a 20% reduction from 28g to 23g. I only have digital kitchen scales with a resolution of 1g.

I measured the exhaust valve head diameters and the 2KR and 3LN are both 15.5mm.

Should have measured all this 20 years ago.

[husaberg]

I don't know the installed height of the springs in the head on the motor. I'll be able to compare the seat pressure to the standard seat pressure of the 3LN head and also what Husa has provided above. It should be pretty simple to come up with a spring shim that should make it work. If the engine in the bike has a lower seat pressure than the 3LN head I'll be able to screw it down until it is equal and that will be exactly the height I will need to shim the spring.

I weighed a few bits tonight and it was very interesting. 2KR/3LN in grams - ex valve 10/10, spring retainer 5/4, tappet 12/8. All together 28/21. Unfortunately the spring retainers can't be swapped as the valve & collett combination won't fit. There is a useful reduction in weight going to the newer tappets of 4-5g or about a 20% reduction from 28g to 23g. I only have digital kitchen scales with a resolution of 1g.

I measured the exhaust valve head diameters and the 2KR and 3LN are both 15.5mm.

Should have measured all this 20 years ago.

i wonder if the measurements i have for the valves which are 3ln and the mid model 1HX are diffrent for 2kr.
Back in the old days when shiming was a aftermarket mod they only used two thicknesses.
there is an ad i could possibly dig up.

[speedpro]

Much simpler solution to measuring seat pressure. I have ordered a pack of flat disc pressure transducers and an Arduino micro. Simply make a bracket that lets me press on the valve with a screw and a flat bit between screw and transducer to spread force. Arduino runs off USB cable to power supply, measures output of pressure transducer and small digital display indicates force. Easy to calibrate by simply stacking a known weight on it and measuring. Handy having a kid who can put a bit of code together and knows his way around Arduino processors.

[husaberg]

Much simpler solution to measuring seat pressure. I have ordered a pack of flat disc pressure transducers and an Arduino micro. Simply make a bracket that lets me press on the valve with a screw and a flat bit between screw and transducer to spread force. Arduino runs off USB cable to power supply, measures output of pressure transducer and small digital display indicates force. Easy to calibrate by simply stacking a known weight on it and measuring. Handy having a kid who can put a bit of code together and knows his way around Arduino processors.

We used to use a old Black and decker drill press and a Scale
The Old drill press was also great for compressing shocks to get out the keepers also.
One like this that held a seperate drill

[speedpro]

Prototype up and running with a variable resistor in place of the load cell.

I had thought of something like that drill press but want to be able to measure the pressure without removing the engine