Got this bike in a swap deal. 5/85 build MC-08. Engine in a tub and more bits to come. Gave it a clean down and off with the heads. Heads are both cracked and valves missing, the bores are a problem with wear and marks from foreign objects. I gave the bores a light hone to clean up the surfaces and was even worse. They will have to be rebored but finding new O/S piston kits have so far eluded me. Have read about using standard Kawasaki ZZR250 pistons and I compared to one I took from one of my ZZR's. Honda piston on rod. Pin dia, length and pin height are the same, but whether the Honda bore can take the 2mm overbore is yet to be determined. The front cylinder rod bearing wasn't too healthy (knock, knock, anybody home) and would have made a horrible noise. The crank pin has a couple of marks but cleaned up with some 800grit linishing paper and is still at std size. Mains are good. So far need to get piston kits, crank bearings, cam chains, valves and gaskets. Feel this could be a long project.
That is grim about the parts. They made the 250 V-Twin for a long time. You would think that os pistons would be available.
Plenty of STD stuff. Have found one .50mm O/S piston, but no rings to suit. Kawasaki has plenty of std pistons/rings. Edit; have found .50mm VF500 pistons but have yet to decide which kidney to sell.
.50mm 2nd os Ring set's x2 , $$56ea https://www.ebay.co.uk/itm/GENUINE-...147075&hash=item1a0694e59f:g:VwMAAOSwWnFWApEe
Thanks for that but CMS were slightly cheaper and am getting their 'gold plated' pistons so added to the pile. Gasket set from UK and bearings (China) on way too. Got two cam chains for Yamaha SR/XT500 or XS650 (same chains and length as VT which are 219FTS x 106 links) coming from Norway. Spending Scomo's bonus to stimulate the economy.
Where in China did you end up getting the bearings. I have rings and bearings that are still in transit. Ordered early feb. Complained Aliba and got my money back . Now looking for somewhere else to by. Thinking AHL.
Looks like you may already have gold plated pistons en route If that's not the case - here's two potential candidates for you http://hispeedpiston.com/ThaiProduct/RacingPiston/RX/RX145461/ There's lots more pistons on this site, however they've re-arranged it, yet again, it is possible to navigate the Thai language menus by hovering and watching the status bar in the web browser which gives the menu items on English Or there is this one... https://www.daytonaindonesia.com/product-detail/ninja-250-62-hi-comp-/30
Happy Easter everyone. @Murdo that link is to your order, which none of us will be able to see. Can you repost with the link to the bearings please? Thanks Frank
Edited post for bearings. Thanks @ruckusman but I could not find any of those with the right size gudgeon pin. Today whilst 'twiddling my thumbs' not being able to go anywhere I started on some small bits to rebuild/check. I filed down the runner ridge of the cam chain guides so the rollers were not touching. The front sprocket seal was still soft and with good 'lips' to the seal so I shortened the inner spring about 4mm and refitted to give a bit more 'grip' onto the shaft. Checked the gear 'dog teeth' and some wear marks on second but consider them to have a lot of life left yet. Blasted the thermostat housing and joint pipe. Checked the thermostat, working ok too. Stripped and cleaned the carbs, replaced some dodgy screws and a couple of missing O rings. With no new parts its now back to 'thumb twiddling'.
Stripped and cleaned the carbs, replaced some dodgy screws and a couple of missing O rings. What O-rings were missing? What main jets were in their?
Just a question about that front rod bearing. Any idea why it was cactus and other rod bearing ok? I have a very similar issue with my little Spada. Crank also ok on mine. Wondering if there is some inherent design issue or just crap bearings. No idea whether they are original or not, but all std size. My cylinder bores appear to be in good shape.
Haven't really looked at it. It had been hammered pretty well as it fell out of the rod when I took it off the crank, ie bent out of shape and not a spring fit into the rod. The other rod bearing has some wear marks so I am guessing that they have some problem with oil supply as both big end are fed by only the right side main bearing. Will be checking the oil pump carefully when I get to it. The chain guides are designed to guide the flats of the chain by using a ridge in the middle. When the guide sides wear down it allows the rollers of the chain to touch and turn as they roll over the guide. Can you imagine how fast those little roller would be turning as they run over the lump in the middle of the guide at redline? This would cause them to wear at a much faster rate then they should and require more frequent chain replacement. By filing the centre down so that the rollers clear (by about 1mm) this will give longer chain life.
Ok. Makes sense about the chain. I had not really thought about it. Spada uses silent link chain, so not an issue. I will check my oil pump also.
I will check my oil pump also. Not sure if the Spada has the same issue as the VT250F. I found the following online years ago when I got my first VT250F. I check the PRV on all bikes I buy. I've done this mod on a couple of VT250F's. @Murdo check the thickness of the washer as I don't put 2x washers in there as suggested. I just replace it with a slightly thicker one. Also, @Murdo don't get too attached to those carbs. I'll give you another set with a standard airbox/filter etc. Those and that custom airbox are from my track bike.
Excellent tip. I would not be surprised if my bike missed an oil filter change at some point during its life.
Agree that the relief valve is in the wrong place, should be after the filter. @Frankster, then you will be happy I cleaned them for you.
Thanks Murdo. I'm learning some valuable lessons on this build you're doing. That tip about the cam-chain guides makes so much sense when you think about it.