GPz305 project bike(s) *with added FAIL!*

[stinkwheel]

Girlfriend has passed her test and is on a restricted licence. Time to find her a bike.

My mate mentioned that he thought the GPz305 he'd had was a superb handling wee bike and just about the right size for her. A check shows them to be putting out 36bhp by the book. A dyno should show that to be 33 or less.

Mates GPz305 unfortunately blew its engine up. A common occurrance with these motors but on his one the BOTTOM end had gone. They usually seize the cam in the head. So, he has a 100% intact bike mouldering in his shed with a seized bottom end and he wants rid of it.

stinkwheel puts out his feelers. Within 2 hours, someone has got in touch as having a ratty 305 project bike which was running when put away. Wants rid of it out of his garage.

Got in the van. Went to mates, picked up his one. Went to bloke, picked up his one, took them home.

So, what do we have:

One late model, low mileage GPz305 with unitrac suspension, belt drive and a seized engine. Superficial cosmetic moulder from being thrown in the shed for four years and not touched. Will need stripping, cleaning and the forks overhauling to put the chassis right.

https://i48.photobucket.com/albums/f216/stinkwheel/305/Image001.jpg
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image002.jpg

One early model GPz305 with twinshocks and chain conversion (handy if the belt lets go). Engine reportedly intact but with considerably more age related problems and general wear such as stripped gearshift splines, lousy wiring and dirty great holes in the exhaust.
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image000.jpg
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image003.jpg

The more observant among you might have noticed one serious problem with a straight engine swap. ie. one is points, the other is CDI.
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image004.jpg
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image005.jpg

Overall. The newer one is a better prospect for an MOT-able bike and I remember the handling being very sweet on the one shot I had of one.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[stinkwheel]

So. Time to get my hands dirty.

Both engines need to be out. At this point I'd like to give a big round of applause to 3 in 1 spray penetrant. Unsticker of rusty bolts to the masses.

Easy enough job. Unhook the secondary drive. Undo the wiring, exhaust, cables and carbs. Three (four on the older one, the more modern one is left to hold onto its own rocker box) frame mounting points. Undo the brackets and slide it out.

https://i48.photobucket.com/albums/f216/stinkwheel/305/Image006.jpg
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image007.jpg

https://i48.photobucket.com/albums/f216/stinkwheel/305/Image008.jpg
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image009.jpg

Puth the frames away for now. I know everything on it will either tidy up or fix from a quick look over. The important bit is the engine.

So. Whip the top-end off the more modern one to see how bad it is. We did post-mortem it at the time and it had done a beauty of a job.

The odd angle that gudgeon pin is sat at is not an optical illusion. The barrel liner is scored to uselessness and the big end appears to have no shells left in it.
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image010.jpg
Well, I knew that anyway. Important bit is the cylinder head and rocker box. There is one bent valve which will need replacing but the camgear is in good nick.

I'm going to give this head to my local engineer bloke and get him to do something with the cam mountings. Either in the form of bushings, bearings or opening out the oilways to prevent the seizure problems this bike is known for. I'll leave it up to him, he used to do roller bearings on old hond twins back in the day so he knows what he's at.

Only stripped one crosshead setscrew removing the alternator cover. The big hammer was for trying to tap it round with a punch. Didn't work. I just drilled the head off and removed the stump with pliers once the cover was off.
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image011.jpg
All looks very shipshape in there. The alternator covers are the same size so I'm pretty sure they wil swap between the two engines. I'm amazed at how simple and lightweight the starter motor asembly is. It's more like the inside of a watch.
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image012.jpg

That's it for today other than removing the clutch cover and plates. I've run into an obsticle in the form of the clutch retaining nut for which I have no socket large enough. I'll pick one up at the car boot tomorrow.

My current intention is to rebuild this engine using the crank and barells from the other one sitting on new mains and with a re-worked head.

I haven't got deep enough into it but I hope I can find out why it seized the big end last time. This would give some peace of mind. I'll be giving the oil pump a damned good going over in any case.

I'm also considering fitting a magnet in the bottom of the filter housing to pick up any cack that's still floating about from the seizure.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[mattgirv]

Looks like a nice bigger bike to learn the ropes on. Mind if I ask how much they set you back for the bikes?

Are you thinking of touching it up much or just getting it on the road and workable?

Grats on the girlfriends pass btw.
____________________
Bikes: 1998 Honda VFR800Fi, 26,500 miles
1989 Honda CB-1, 38,000 miles

[stinkwheel]

[virus]

I suspect my manual for those z250 twin lumps we spoke about also covers the 305, if you need any info then let me know and Ill have a butchers for you mate.


Cheers
John
____________________
own: 81 xs1100g...
owned: 85 rat CG (sold), 91 GS500e (stolen), 84 gsx400f (scrapped), 81 z250 (siezed, siezed, scrapped), 83 cb250rs (sold), 84 gpz750r ratfighter (killed) 84gpz400 (sold), '80 cb650 ratfighter (wrote off) 95gsx6/12f ratfighter (killed) 91 xj900 (sold)
stinkwheel Well I just had my hands up a pigs fanny. Which makes your concerns pale into insignificance.

[stinkwheel]

[Gazdaman]

Don't hang about do you?!

Nice job, look forward to seeing the finished product. Splitting cases has scared me ever since changing the MZ crank, and that was easy!

Gaz

[stinkwheel]

[FreshAL]

[stinkwheel]

[stinkwheel]

Oil pump and oil strainer are off now. The pump is really neat, one of those trochoidal ones.
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image023.jpg
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image024.jpg

From reading about, the guaze strainer on the oil pump inlet is the cause of many of the problems with these bikes. It gets easily blocked meaning no oil gets fed to the top end.

I'll need to come up with something to counter this. Probably fitting a bigger bit of gauze so the oil can run through it rather than being forcibly sucked through it (wedging crap in the gauze as it goes).
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image025.jpg
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kickstart]

Hi

I am shocked that the oil pickup is so small.

What do they use as an oil filter. A cigarette filter tip?

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[stinkwheel]

[Kickstart]

Hi

A funnel, with gauze over the wide end, with a genetle curve instead of an angle from the funnel to the tube.

When you say it goes through a blind section of the sump, do you mean that the pickup itself is located in the sump and points up with the gauze end on top? If so making the gauze longer might cause issues if the end is higher than the oil level (suspect it would then just draw a load of air into the pump after a short while of running).

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[stinkwheel]

[Kickstart]

Hi

Trouble is anything going through the pump will damage it, hence the need for the gauze to stop large lumps.

Looks like you might be able to extend the gauze another cm or so.

You currently have ~16cm square area of intake (4cm long, 1.2cm diameter, including the end), gauze covered. 5 x 6mm holes would only give an area of ~9.5cm square.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[stinkwheel]

I suppose I could also just change the oil every 2,000 miles and make sure I clean the gauze every year.

It's done 16k miles and it isn't THAT dirty. Judging by the screws holding the oilpump on, it hasn't been done before.

EDIT:
I was taking the intake area as the narrowest point, which is the end of a 12mm diameter pipe, 113mm sq. If I took the gauze off altogether, all the oil still has to pass through this. Maybe this is wrong?
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kickstart]

Hi

Not sure on the oil change interval, but it only takes 1.8 litres. However even Superdreams were meant to have 1800 mile oil changes and they had a reputation for being far tougher. Would do it rather more often than that.

[stinkwheel]

The area of gauze is adequate to allow oil through. The problem is it is very prone to becoming blocked with crap out of the bottom of the sump.

The effective surface area of a blocked gauze being zero, seizure ensues.

The main problem seems to be that the end of the pipe is very near the bottom of the sump and acts like a vacuum cleaner, sucking all the crap into the holes in the gauze.

My initial thought was to make the gauze bigger so it sits that bit further away from the end of the pipe and hopefully doesn't get as much crap lodged in it.

On consideration, Anything I did along those lines would prevent me removing the gauze for cleaning without splitting the engine.

In an ideal world. The intake would be a bit further off the bottom of the sump which was my idea with the pipe with holes in it. If I can get it to somehow suck the oil down into the pipe rather than horizontally, I'd have overcome the design flaw.

I'll have a play with some microbore pipe tonight.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[stinkwheel]

Project on hold.

Started stripping the second engine:

https://i48.photobucket.com/albums/f216/stinkwheel/305/Image028.jpg

https://i48.photobucket.com/albums/f216/stinkwheel/305/Image029.jpg

https://i48.photobucket.com/albums/f216/stinkwheel/305/Image030.jpg

https://i48.photobucket.com/albums/f216/stinkwheel/305/Image031.jpg

https://i48.photobucket.com/albums/f216/stinkwheel/305/Image032.jpg

And that piston has taken out the small end too.

Engine #2 status = FAIL
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Endless Nameless]

[Kickstart]

[stinkwheel]

[Kickstart]

Hmm, might be worth having a word with someone like SEP and see how much they would charge to sort the crank out (possibly sticking a bush in the little end).

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[stinkwheel]

Well an update.

I'm a little short on photos for now but I'll add some later once I can get them off my phone.

Managed to find another engine off a guy on ebay.

It was looking worn so I stripped it down too. As well I did because the valve stem oil seals were on their way out and it had a known oil leak from the gear shaft oil seal (which requires a special tool to replace the shaft in without damaging it).

Anyway. Got the crank out of it, decent set of barrels and pistons.

Comparing the cylinder heads, the one off the original belt drive bike looked best. I took all the valves out to replace the oil seals. As well I did because BOTH valves on the right hand side were bent.
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image033.jpg

I pinched two valves off the new engine and lapped them in using an electric drill. I then polished the head and barrel mating surfaces using a sheet of glass with fine grinding paste until they were a uniform consistancy. I find this an oddly theraputic task.
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image034.jpg
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image035.jpg

Having cleaned it all off thoroughly with multiple changes of paraffin then spray brake cleaner so there was no trace of grinding paste, I set about reassembling.

All went pretty smoothly. I got some fancy non-setting liquid gasket for joining the crankcase halves rather than pay through the nose for kawabond. All went together in a pretty incident free manner.
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image037.jpg

Here is where I screwed up though. I was making sure the crank turned ok once it was all torqued up and managed to chip the edge of a piston against the crankcase.
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image038.jpg

Enquiries revealed a piston kit to come in at £80 so I bodged both pistons with a hand file so they can't propogate any cracks. I've since tracked down some Z650 pistons, I'll get my mate to bore out one of the knackered sets of barrels to suit (taking it out to 325cc) so I have a spare.
https://i48.photobucket.com/albums/f216/stinkwheel/305/Image039.jpg

Installed the barrels and head with a minimum of fuss, timing was a piece of piss. Rocker box was slightly fiddly bacause you need to hold all four rockers up with your fingers through the inspection ports as you fit it. Using the same liquid gasket to fit it.

The rotor was a bit of a pain to fit because of the starter clutch preventing it sliding straight onto the Woodroffe key. Starting half a turn out and turning the crank as you push it on seems to be the best option.

Manual says the clutch basket is supposed to be tightened to 85ft/lb. I really don't see how this is possible, even with the proper clutch holding tools because a strap wrench isn't going to hold that. It'll have to make do with 50ft/lb because that's as tight as I can manage, it's got a lock washer so it's not going anywhere.

Found an absolute whopper in the haynes manual where they've put foot/lb where they meant inch/lb for torquing up the clutch plate bolts. Just goes to show tou still need to apply common sense: "Hmm, so should I be using my big 1/2" drive torque wrench turned to the same setting as my transit van wheel nuts for these M6 bolts going into a thin aluminium casting?"

Took minutes to get it fitted into the frame once assembled, covers on, oil in.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.