Building a new engine

[Snails]

to creat a port map, you are essentially measuring the distance between the top of your barrel, to the top of the exhaust and transfers, and the bottom of the inlet. The best way is to insert a roll of card/paper, and shade over the ports. the edges of the ports will show up, allowing you to measure down. The shape and width and area also comes into play, but maybe thats for another day. Use Eden's fantastic online calculator at lambretta images archive (google it) and put in all your figures to work out the timings.

Thanks, sounds easy enough to give me a rough idea as to whether I need to do any work. Hopefully will find time over the next few days to give it a go. Ideally they will be ok anyway and I can leave alone - I'll check out how rough the edges are too.

I'm interested in your comment regarding con rod length as I'm planning on replacing this item, and Ive read before that a longer con rod gives a smoother engine but I'm not quite sure what people mean by this and what the advantage is. Do you mean the power is more evenly distributed over the rev range? Changing to a longer rod does not give more power does it. The opposite would be a engine that delivers power more in certain rev ranges than others? This might be ok depending on driving style or environment ? I tend to drive in urban areas and rag the arse off it if possible. Its kind of fun.

Also I don't think I will be changing to another kit if this one does not work out that well. No money for that! Also I'm sure if I keep to my objectives it will be fine. The increase from 150 to 175 in itself should give me a nice difference in engine I'm thinking. At the end of the day reliability is more important to me than power which is why the small improvement to a safe 175 appeals.

[olliewtf]

stick with the sr barrel, you have so many possibilities with it! the crank choice being one. Its only something i recently took an interest in; yes its true, conrod length doesnt give you more power. I wish it dead cause that makes sense in my head! some people follow the ruling that the stroke should be the conrod length halved, a la tv 175, 58x116. However, there are so many exceptions that I dont think this is a thing anymore... and why it gives you a smoother engine well, i dont have a scientific answer. it just does aha. I always assumed it meant less vibration; theres other factors to consider too, shorter conrods allow the piston to rock in the bore more (i think?) but this is all getting rather technical. Either way I see it as an advantage.
Im opting for a 60x110 for my conversion. the 60mm does give you more power. Ive found that glasgow lambretta stock the MEC ones for around 130 with a skf mag bearing. that to me is a bargain.

[Snails]

Ok, I've kindly be walked through how to get a rough determination of the state of tune of the barrel I have. My plan is now to part assemble and double check the figures. At this point I'll decide whether I am up for making any modifications to the timings. I've also spent a bit of time to look to see if its worthwhile my time matching the engine casing to my barrel's transfers but to my eye there seems little point. The base gasket fairly evenly matches the engine case as it is and there's not much trimming needed to match it to the barrels transfers. The one thing I was thinking about was smoothing out the areas circled in red








also I've been a bit shocked at how much all the parts I need to complete the engine have added up to. I'm still shopping around to try to work out whether I can shave some money off this (without shrimping on quality) and still need to contact a local bearing seller.

One question for now. If (and its still quite a big if at this point) I did want to tweak my port timings how do I go about marking the area I want to remove? Or do you need to do this by eye and lots of remeasuring?

[Snails]

Having just refitted my exhaust, two things crossed my mind.

1. Roughly how many miles would you expect an exhaust to last for. Mine has done maybe 8 - 9 k. Its looks the worse for wear as do many pipes but I dont plan on replacing it. Having said that if I can expect it to pack in relatively soon then its maybe worth planning for.

2. I'm sure I've remember seeing some sort of kit or modification to make down pipe removal easier. Or did I just dream this?

[olliewtf]

in terms of your port timing measurement when cutting, you can get a metal scribe for a few quid to mark what you need to cut. I would still do this in stages though, ie cut a bit then measure, run through port calculator then measure again. as for the transfer entries on the barrel, if i were you leave them as be, if they match fairly well any gain here will be marginal; also the two parts in red, thats up to you, certainly smooth them but be wary of how close they are to the barrel studs, you want this bit to seal nicely.
the only kit im aware of for ease of downpipe removal is the bridge fixing it that allows easy removal of the bridge and rear runners.
My exhaust is 20 years old. probably needs a decoke but hey.
Good luck!

[scooterslag]

Regarding the crappy SIL bearing cranks- I've been in touch with Martin at Chiselspeed and he can convert the bearing to either a standard steel cage bearing for £35 or a silver plated bearing for £42.95 + £10.20 for P&P, mines off to sunny Leeds next week, hope this is some help to people like me getting by on a micro budget but don't want to scrimp on quality

[shocky]

Regarding the crappy SIL bearing cranks- I've been in touch with Martin at Chiselspeed and he can convert the bearing to either a standard steel cage bearing for £35 or a silver plated bearing for £42.95 + £10.20 for P&P, mines off to sunny Leeds next week, hope this is some help to people like me getting by on a micro budget but don't want to scrimp on quality

I had a better longer rod fitted to mine and shims fitted by HB but thats a good price

[storkfoot]

Ed, just thought I'd share a few thoughts as I've tried most things you refer to:

Gaskets on box type exhausts - I never had any success with annealing copper gaskets. They just leaked. In my experience with all the others, the MB ones with 4 stud holes have been the best but you can't re-use them and the exhaust has to be a good fit ie the manifold precisely parallel and not pulling slightly one way.

SR barrels - I appreciate that you are working to a budget. You must check the timings otherwise it'll just be pot luck as to whether it works efficiently. I ran mine for quite some time as a 175 and then a 185 but I was never really happy with it. Only when I got it road tuned by someone who knew what they were doing, did it become a joy to ride. The steel liners wear out quite quickly though.

Conrods and big end bearings - if you are over "our side" Grampians in Crosby should sort you with a decent Yamaha conrod and big end bearing for a very good price. Both my cranks have been built there (Indian GP 200 webs, Kawasaki [110] and Yamaha [115] rods) a few years ago now, in the case of the Kawasaki one). Both engines are, IMO, pretty smooth and relatively vibration free.

Hope this helps a bit rather than add to the confusion of differing opinions

[goldeneye]

when you"re annealing copper gaskets, heat them to cherry red, and then plunge them end on into cold water, not flat into the water, as this causes them to warp. end on and they should keep their flatness.

[Snails]

Ed, just thought I'd share a few thoughts as I've tried most things you refer to:

Gaskets on box type exhausts - I never had any success with annealing copper gaskets. They just leaked. In my experience with all the others, the MB ones with 4 stud holes have been the best but you can't re-use them and the exhaust has to be a good fit ie the manifold precisely parallel and not pulling slightly one way.

SR barrels - I appreciate that you are working to a budget. You must check the timings otherwise it'll just be pot luck as to whether it works efficiently. I ran mine for quite some time as a 175 and then a 185 but I was never really happy with it. Only when I got it road tuned by someone who knew what they were doing, did it become a joy to ride. The steel liners wear out quite quickly though.

Conrods and big end bearings - if you are over "our side" Grampians in Crosby should sort you with a decent Yamaha conrod and big end bearing for a very good price. Both my cranks have been built there (Indian GP 200 webs, Kawasaki [110] and Yamaha [115] rods) a few years ago now, in the case of the Kawasaki one). Both engines are, IMO, pretty smooth and relatively vibration free.

Hope this helps a bit rather than add to the confusion of differing opinions

Do you know I think I might be basing my whole engine on some advice you gave me years ago on the LCGB forum. Think I have taken my gearing carb set up and port cleaning up idea from that. I've checked my timings but I'm not putting them up until I've checked them on the engine. No point starting that debate until then.

They are fairly boring at the mo.

Is Grampions in the Crosby / Waterloo area? My Mrs is from Neatherton so I know the area well. We are not exactly seeing eye to eye at the mo which is why I have time to build my engine but no money to do it with. Still im sure I'll be over that part for some reason or another and its only an hour away. Food for thought.