Mtc big bore kits

[Coleman]

Hi people, just wondering if anyone has any experience of Mtc big bore kits for an 1150 efe . I’ve bought a 1260 kit and was wondering if there was any tips for this kit . Thanks in advance

Edited November 19, 2022 by Coleman

[arnout]

By now I reckon I've done some 45.000+ km on my EFE since installing a 1327cc MTC piston kit along with a resleeved stock cylinder block. To my surprise these km's have been without any issues concerning the pistons. The starter clutch has suffered a bit though to overcome the high compression. (I machined the original piston domes down a bit to reduce the compression ratio from a listed 13.5:1).
Oil consumption has been steadily rising the past few years, pointing to possible worn piston rings. But as the valve guides were already pretty worn when I installed the pistons, the valves seals will at least be responsible for a part of the oil level dropping.
Only recently I tested the compression and found a slight difference between the inner and outer cylinders, which may as well be attributed to poor valve seat sealing as opposed to worn rings. (Readings of 15-16 bar seemed a bit high, but the gauge is probably only suitable for comparison between cylinders)

As for tips I reckon normal rules apply. Check the right clearance for boring. (Ask a more knowledgeable person!). Compare the weight of the pistons, and try to make them the same, as mine varied quite a bit. (Perhaps because I machined the domes). Check deck height and "squish" by doing a dry build (without rings). Use the base gasket to correct this at first. Having the head or block surface milled helps a lot with head gasket sealing and will affect the deck height as well.
Anything over 1230cc requires larger sleeves. Boring to 78mm to house a 1260 kit is pushing your luck, but you may get away with it. (A cracked sleeve will need to be replaced) . MTC and others recommend using a "big block" to house these larger sleeves. As stated mine is a resleeved stock block I found on Eblag for cheap. It was cheap because the block was cracked on one cylinder (probably during installing the sleeves). Despite a dodgy fix to correct this and constant oil weep because of that, it worked perfectly well otherwise. Using a stock cylinder block instead of a "big block" helps a lot with cooling, but -obviously- isn't as rigid as a "big block".

[Reinhoud]

I've got a 1247cc big bore on my GS1000, with mine I had to put some liquid gasket around the sleeves / cylinderblock.

The O-rings didn't fit anymore. Used an artist brush to get it where I wanted it.

 

No clue how this is with different brands

[Reinhoud]

No clue how it goes with a GSX engine, but with my GS engine I had to remove material from the crankcases to allow for the bigger sleeves.

I made a disc, one side had the diameter from the stock base gasket, the other side had the outside diameter of the bigger sleeves.

Put the disc and the base gasket over/on the crankcases, draw a line on the crankcases, and start removing material with a barrel grinder.

This is slow process, took me about an hour per cylinder.

 

With this disc you can also draw lines on the geasket to cut it out to the right size to use it on the cylinders. To cut it out I use nail clippers.

[rodneya]

Any progress with this? Are you installing new sleeves?

[Maggotbreath]

On 12/17/2022 at 3:57 AM, Reinhoud said:

No clue how it goes with a GSX engine, but with my GS engine I had to remove material from the crankcases to allow for the bigger sleeves.

I made a disc, one side had the diameter from the stock base gasket, the other side had the outside diameter of the bigger sleeves.

Put the disc and the base gasket over/on the crankcases, draw a line on the crankcases, and start removing material with a barrel grinder.

This is slow process, took me about an hour per cylinder.

 

With this disc you can also draw lines on the geasket to cut it out to the right size to use it on the cylinders. To cut it out I use nail clippers.

Dam good idea! I paid good money to have a crankcase machined, it's a dam nice fit but could have DIY instead!

[Reinhoud]

On 1/25/2023 at 10:52 AM, Maggotbreath said:

Dam good idea! I paid good money to have a crankcase machined, it's a dam nice fit but could have DIY instead!

Machinein is most likely the better way to go, if set up correctly there's probably less material taken away.. At least it looks better.

 

 

But you need to have a machine shop what's willing to put some effort in it...

 

 

 

Edited January 26, 2023 by Reinhoud

[Gixer1460]

18 minutes ago, Reinhoud said:

But you need to have a machine shop what's willing to put some effort in it...

For a good machinist, its not a big deal. Probably the longest operation is getting the top of the case parallel to bed of the machine. Centering the boring head on each bore is pretty painless. Agreed though that machining is the way to go for tighter fit. If, for example you took your case now to a machinist, say, for bigger sleeves, the job would be more complicated due to the DIY metal removal not leaving a uniform concentric circle to centre the machine on - pros & cons!

[Reinhoud]

6 minutes ago, Gixer1460 said:

For a good machinist, its not a big deal. Probably the longest operation is getting the top of the case parallel to bed of the machine. Centering the boring head on each bore is pretty painless. Agreed though that machining is the way to go for tighter fit. If, for example you took your case now to a machinist, say, for bigger sleeves, the job would be more complicated due to the DIY metal removal not leaving a uniform concentric circle to centre the machine on - pros & cons!

Installing the case on the tables is not as easy as it might look I think, it has to be on the right angle