Engine rebuild

[Einstein]

Hi guys...

Normally I'm giving help, but I thought I'd spin this one around and get some opinions..

Did a compression test before I started to strip it, and although the engine has been stood quite a few months, I got the following readings.. (psi)
1, 130
2, 125
3, 105
4, 120

after putting a few drops of oil down, the readings didn't change much, so I don't think it's worn out.. but the valves probably need doing anyway..

Took the head off, and noticed a fine score line on cylinder1.. and this one has the highest compression.. it is very fine, but you can just feel it with your fingernail.. I will presume this will be ok, and a light hone and a new set of rings will be beneficial. doesn't feel like any wear ridge at the top of the bores.

I was considering renewing the camchain, but there is about 3/4 inch left of travel on the auto tensioner plunger.. enough?

Also noticed the starter gear behind the generator has a crack, so I will swap this over from the spare engine..


So, your opinions gentlemen..



John

 

[gearhead13]

Where are the pictures???

 

[Guest]

How many miles on the bike/engine?

With those readings I woulda tried to run it but..Too late now.

 

[Guest]

A scratch you can feel will probably require oversized pistons.
I would split the cases to replace the cam chain.

To spec a cam chain you measure the length between a certain number of link pins.

Remove the valves and check the seats and valve for pitting. Replace the valve stem seals.

 

[tejasmud]

Well, you are in this far. So, you might as well do it right.

Check the tolerances on everything, replace what is out/if out, replace gaskets and seals, and put it back together.


Oh, don't forget lots of pictures. We like this sort of stuff round here....

 

[kta]

Agreed! Pics please!

Chances are if you took those compression readings warm after circulating some oil though the system they would have gone up quite a bit. None of them are 'terrible' but 105 is certainly getting down there. If the cyls look reasonable aside from a mark or two you'll probably be in great shape just giving them a light hone and installing some new rings. But depending on the mileage the valves are definitely worth and inspection.

What is the mileage? out of curiosity.

 

[Einstein]

Hi Guys..

Thanks for the opinions so far... interesting

I've taken a few pics but nothing much as yet... I need to get the other engine stripped to see how bad that one was/is... that had 60 psi the last time I checked, and still ran sweet.

Started to get the crud off the pistons and clean it up a bit..
The clutch looks in good shape, as does most other parts.. although if any are in better condition on the other engine, I'll swap them over..

I've attached a pic of the bore... doesn't look that bad really.

I'll update this thread as it goes on.

John

 

[hampshirehog]

That marks are nothing to worry about - granted it shouldn't be there but I bet you a pint it won't make a gnats worth of difference. Just give the bores a light hone (don't aim to remove the marks if it needs 'more than a light hone') and if your rings are well within spec (or pop in new ones) you should be good to go. Cheap NOS rings with BIN on Ebay at the moment by the way (or there were yesterday).

Chef is right about how to check the cam chain. Unless your bike has been to the moon and back chances are it'll be fine.

The 105 compression figure is ok on its own but it's a bit unbalanced with the others (being 25 away from your best). If you're honing / ringing and sorting the valves though I wouldn't worry. When you've rebuilt the motor take the bike out for a good hard ride and it'll sort itself out.

 

[Einstein]

Mileage wise, I haven't a clue...
The bike has had lots of previous owners, and I have replaced the clocks, and engine.. which aparently came from a bike with less then 40K miles.. but who is to say that is the true mileage..

There doesn't appear to be a lot of wear in the camchain, and as I am going to replace the rings, I'll save a bit by reusing it.

Another thing I noticed, is the pistons have been numbered inside the skirt, so it's definitely been stripped before.. hopefully not by the PO, who put the cams in backwards

The pistons are not stamped as oversize, and I'm struggling at the moment to find std size rings, other than originals from the dealers, and overpriced ones from elsewhere..

EDIT: Just going to add... Suzuki dealer in the UK.. $69.31 each set... Babbits $23.26 a set.. and cycle parts nation are $21.81 go figure !! but they want $111 shipping for 4 sets ???????? WTF


John

 

[hampshirehog]

Have you tried Robinsons Foundry? They've bought Spares Direct entire parts stock I believe so I guess they'll have some in stock and they price pretty reasonably. There's Govnorsbridge as well if you haven't tried them.

BTW - the Ebay rings I spotted yesterday were OS and went for ?14.20 a set.

You could ask one of the US guys to handle the rings for you and post to the UK at the proper price as well. CMSNL also carry the sets at 32 Euros each and they don't rip off on the postage.

 

[Einstein]

Hi wally,

The UK price was from Robinsons... ?42.34

Govnors don't have std, only oversize, and I think the only ones that are on ebay are also oversize... the std ones I saw a while ago were only one set.

I got the right side exhaust from Govnors... good price, and a quick delivery..
They were loking for some other bits I asked for, but didn't get back to me.. I ended up buying from Marcel in Holland.. www.suzukitandgtparts.nl seems a nice chap.

John

 

[Einstein]

I eventually got the rings from Cycle Parts Nation.... plus a few other bits and pieces while I was ordering.. they did me a good deal on the postage as well.

Managed to lightly hone the cylinders, and fitted the new rings... getting a good slurping sound when turning the engine round, and all seems good so far..
ground the valves in today, and they look in good shape..

I'm not going to build the engine up yet, but do it once I get it back in the frame.. should be much easier, and avoid scratching the powder coating.

Plenty to do, not much time to do it now that I got a new job !


John

 

[Suzuki mad]

Uk prices are quiet high. You can save going to the States but watch out on Customs duty and Royal mail charges as that takes what you save.

 

[Einstein]

So true...... luckily, they agreed to mark the value as $50, so the total cost of duty and VAT was only about ?8, but they did put another ?8 of service charge.. (Parcelforce)
It should have been much higher..

 

[TheCafeKid]

So true...... luckily, they agreed to mark the value as $50, so the total cost of duty and VAT was only about ?8, but they did put another ?8 of service charge.. (Parcelforce)
It should have been much higher..

Wouldnt spin the motor too much til you get it back together. The hone edges are supposed to be razor sharp to help bed the new rings. If you spin it over too much before break-in time, you might wear the edges down to the point they never seat up properly, or take an excessive amount of time to do so, in which case it will be a "mosquito killer" untill they seat..

 

[Einstein]

yeah.. It'll sit there now until it goes back in the frame.

On another note, I may have found a supplier for some engine paint that will be a perfect match to the original... they have some listed for a 1981 GT250 (X7) that I think might be a bit dark, but they said they could match a sample... that's if I can find any remaining after stripping the black paint off.


John