Interesting , explains why the zxr has the largest size jets and a very lumpy idle. Had a quick play around with that website and it seems that the zxr has the largest cams followed by the gsxr250, then the fzr and lastly the cbr250 with the smallest cams
I did think about that. I would need to find a bike with similar cam profiles, rob the servomotor and its computer, and probably fabricate a completely custom exhaust and butterfly valve. Figure out how to get the RPM signal from the pickup (or TCI?) into the servomotor's brainbox. Then it may need dynoing and jetting changes. Certainly a lot of work, but doable. Can you share the details on the valve timing for those bikes so I can have a look at it, thanks.
Kawasaki usually do tapered exhausts to deal with low down torque issues. I did the same for my FZR400 and threw the Exup away.
The ZXR headers are tapered smaller as they get closer to the exhaust ports, if that's what you mean.
I have always done it the other way, worked for me. The ZX10 pipes in the pic are obviously larger at the port.
What's the bracing for? Does having a stainless steel exhaust make a difference? EDIT: Sorry, I thought these were your FZR400 exhausts.
Here you go @Linkin Gsxr250 Overlap 76° Intake Duration 290° Intake Lobe Centre 107° ATDC Exhaust Duration 276° Exhaust Lobe Centre 100° BTDC Lobe Separation 103.5° (Cam°) Fzr250 (3ln1) Overlap 62° Intake Duration 276° Intake Lobe Centre 103° ATDC Exhaust Duration 268° Exhaust Lobe Centre 107° BTDC Lobe Separation 105° (Cam° Cbr250rr (L) Overlap 30° Intake Duration 232° Intake Lobe Centre 97° ATDC Exhaust Duration 227° Exhaust Lobe Centre 102.5° BTDC Lobe Separation 99.8° (Cam°) Honda lists their cam spec at 1mm lift . The others don't specify so i have a feeling that's why it looks alot smaller than the others?
@Frankster They are Ti as standard. I'd be crowing from the rooftops if I made those. Don't know what the braces are for and stainless is noisy.
Interesting. I just swapped my muffler from a straight through back to standard and noticed the standard had an offset exit pipe. I figured this was for the echo effect to help the low-mid range. But having ridden it, I found the mid range to be very poor and the low is better. Given how far along the pipe this is, it makes sense that this is for the low end. My suggestion: go a straight-through muffler, and retune the carbies. My bike would sit on 6,700 at 100kph in top gear before, but now top gear (which is like 8th because 4th gear is the same ratio as standard gearing 6th) is unusable. It also sounds awesome and can be heard for miles! :-D The problem I had was too rich down low, too lean up top. They are the smallest pilot jets for those carbs, so new needles might help, but after what you said about overlap, that might be the issue, rather than rich. Bigger main jets might be enough. P.S. fight that feeling to buy a new bike! It's a slippery road, filled with hope (wishful thinking) and disappointment. You've got a very nice bike (especially given the work you've put into it). If you want something exciting, buy track days!
Alright, some progress! I pulled the bike down to access the cylinder head and barrels. While they are off, I decided to service the carbs again. Pulled all the jets and chucked them in the ultrasonic. Float needles have had it, as have the o-rings on the seats. Removed the radiator and exhaust, then pulled the valve cover to check the clearances and later pull the cams & tensioner. Exhaust clearances are out (tight), inlets are tighter than when I set them last but still within spec. Tensioner has been noisy, but still no marks on the inside of the cam cover. The manual unit I bought does not fit (offset bolt holes and tensioner bolt is far too long) Main rod has some polishing/wear on it Work will be doing the engine work (under this apprentices' supervision ) and I will put the bike back together. So for now, I am the "proud" rider of a BMW G650 GS one lunger, one of works' loan bikes.
Colleague at work got the honour of breaking the motor apart. What I found interesting is that the head bolts on these are actually bolts, unlike the FZR250 where they are studs protruding from the block. Motor apart, clearly not running perfect, but not the worst I've ever seen. I noted a lack of burnt oil / blown gasket smell. When checked with petrol in the ports, all the valves were leaking. #4 was particularly bad. So they will all come out for a clean, lap the seats, and new valve stem seals. Note the thermostat in the centre, the bleed bolt is on the right hand side (flipped in the 2nd photo) Cylinders off, all big ends checked out OK Looking at the head, #1 through to #4 A look at #1 piston, the rest are pretty much all like this. Nothing past the oil rings which I am glad to see. Fingernail test on the skirts = passed. Yet to have a proper look at the bores, but they look OK so far.
Does the ZXR run the crankcase breather hose up through the air box by any chance ? I've seen a few engine's that have that system and the piston's looked black with crusty carbon and burnt oil on them like that, also happens with a dirty air filter with a dodgy air filter seal.
Yes it does. There is a rubber tube in the airbox that sits over a protrusion on the crankcase. The airbox sits directly on top of the cases so there is no easy alternative.
Finished my shift at work at 3pm so spent a few hours cleaning bits, and got all the valves out. Washed the barrels as per last time with the FZR250. Strong mix of CT-18 and hot water, wipe with a white rag until clean, oil to stop flash rusting. These marks concern me, but all passed the fingernail test. They are on #1 and #4, and it looks to be where the ring ends were. The oil ring ends on #1 were lined up, and the end of the spring wasn't too far away either Other than that, I can still see the cross hatching and they appear OK. Nothing measured yet as that what I'm paying the workshop for Traced an outline of the head onto some cardboard and starting pulling the valves. The tool was far too big so removed the end and fitted an open 13mm socket, worked well. Some of the springs have a curve to them, so I'll just replace the lot of them. Valves are yet to be looked at in detail, but from the one I looked at, there is a lip on them. I'll let work make the call, but will budget for a set of 16 new valves. Valve seats. Inlets are fairly clean, exhausts are garbage. No wonder they were leaking. Exhaust ports - yuck Dunked the head in CT-18 and hot water, gave it an external clean and wiped the exhaust ports with a rag while wet. Soooo dirty. Decided to toss the water and let it sit overnight. I pulled off the thermostat housing and removed the thermostat. The gasket broke away as soon as I tried to move it, so I'm up for another one. Pistons, I cleaned the faces carefully on the wire wheel, and dunked them in the ultrasonic for the day. I reckon they need some threebond treatment