spawningvat Posted September 24, 2012 Share Posted September 24, 2012 Hello Everyone: So I have a little project on my hands, and I'm looking for some help and advice. I just got a 94 750 with about 23000 miles on it. It had been in an accident, so its missing the entire fairing and headlight assembly, the tank is rashed, and rear plastics are rashed and cracked. It runs, but has a very noticable metallic tapping to it. I was betting on valves, but I popped off both valve covers and all were in spec. Checked spark plugs, and they looked good. When I start it, all 4 exhaust pipes get similarly hot, so I'm getting compression and ignition on them. So...I drained some oil into a white container, and that's when I saw it! Bits and pieces of shiny metal...ugh! They are ferrous, says the magnet that dragged them around the bottom of the container. Anything else that the metal could have come from? What material are the bearings made from? How likely is a spun big end con rod bearing? I'm pretty good at fixing stuff, just not this big (read: lawn mowers, weedwackers, chain saws); if I remove the engine, flip it over, and split the cases, is there enough space to access the broken rod bearings to replace it and still keep the crank in? Is the crank likely to be shot? I don't want this to turn into a money pit... Worst case scenario, I swap over wheels, tires, brake rotors to my 99, and part the rest. BUT...it would be awesome to rip into it, slap in some new bearings, and turn it into a rat bike. So, lets hear some thoughts! I'm heading out there now to see if I can figure out which cylinder the knock is on. /s/ Sean (Correction, bike is a 1994 model, says the title) Link to comment Share on other sites More sharing options...
spawningvat Posted September 24, 2012 Author Share Posted September 24, 2012 Update: Pulled the clutch side cover, and could see #3 and #4 con rod bottoms through a hole. I pried at #4, and it didn't move. I pried at #3 and it moved approximately 2mm back and forth and up and down. There's the problem! So, original questions: Is there space to change the bearings from the bottom, leaving the piston and the crank in the engine? Even more important: How likely is it that the con rod journal on the crank is shot? New question: Any one have a 4th gen bottom end they would like to part with? My top end (head, valves, carbs) is in good working condition. Link to comment Share on other sites More sharing options...
Member Contributer mk2davis Posted September 24, 2012 Member Contributer Share Posted September 24, 2012 Do you have a copy of the service manual? I haven't done any enigine work on 3G, but the manual may answer some questions for you. Link to comment Share on other sites More sharing options...
samaki Posted September 24, 2012 Share Posted September 24, 2012 You can Ebay a complete engine for $500 or less. Last 3rd gen I bought was less than $200! That is likely the best way to go. By the time you swap your top end to another bottom you will have a few hundred bucks in gaskets and seals alone. Link to comment Share on other sites More sharing options...
Guest Posted September 24, 2012 Share Posted September 24, 2012 I think I would try to chase down a used , complete motor- might be the least expensive option. Link to comment Share on other sites More sharing options...
spawningvat Posted September 25, 2012 Author Share Posted September 25, 2012 I've downloaded the service manual and have studied it. It looks like i can reuse most of the bolts. Will need new gaskets, and bearings. I'm hoping to pull the engine, flip it over, rotate pistons to a midway point, remove con rod caps, remove crank, polish journals, put new con rod bearings in, and reassemble. Does that sound feasible? (Hoping to get around head removal and piston removal.) Thanks guys! Link to comment Share on other sites More sharing options...
Baileyrock Posted September 25, 2012 Share Posted September 25, 2012 If you have a Junk engine(any damage) which is very unusual as the VFR V4 is known as the most over built/over engineered engine ever built, then as mentioned I would buy a used motor vs working on one that someone trashed somehow! Besides it's HIGHLY unlikely that the crank journal could simple be Polished out! BR Link to comment Share on other sites More sharing options...
NakedViffer Posted September 25, 2012 Share Posted September 25, 2012 I agree with everyone else, replacing bearings without full dis-assembly is always a bad idea. You don't just replace bearings like that, its not a headgasket.. The bearing spun for a reason, and without diagnosing and addressing the problem you're asking for trouble. Re-using critical fasteners is a gamble too.. The motor in my bike right now is one that came from ebay for $500 shipped to my door, it ran like a top when I got it, and I've beat on it heavily from day one, never had a problem. Save yourself the headache, buy a motor, bolt it in and ride. Link to comment Share on other sites More sharing options...
Member Contributer Dutchy Posted September 25, 2012 Member Contributer Share Posted September 25, 2012 Degrease the junk engine, place a perspex sheet on top,you will have a nice side table next to the couch to put your beer and popcorn on! Link to comment Share on other sites More sharing options...
spawningvat Posted September 26, 2012 Author Share Posted September 26, 2012 Ok, so the general consensus is that the engine is gone. Damn. Looks like I'm in the market for a 4th gen engine. Anyone know anyone? Link to comment Share on other sites More sharing options...
Guest Posted September 26, 2012 Share Posted September 26, 2012 What I have noticed in bikes without tip over switches, is when they crash the engine is usually wide open while the rider is stumbling around in the grass. Engines don't seen to get good lubrication when they are on their side or upside down. This could have beeen the cause of your engin failure. Not sure about your area, but I see forth gen VFR often for under 1000.00. If it were me, I would buy another running crashed bike and get the parts which I need. Once you have your bike whole, part out the donor bike on Ebay and you will get a good chunk of your mony back. I have been able to, at least break even with this method... Don't plan on making a profit and you won't get depressed. I love my forth gen. Link to comment Share on other sites More sharing options...
tailgunn Posted September 26, 2012 Share Posted September 26, 2012 I have a motor I should probably part with...Was gonna make it a track bike but I really shouldn't spend the money on it. PM me for details. I probably have other parts that will help you too, like a tank, fairing bracket...maybe some fairing parts. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.