Exhaust Change

[soullad]

Wise move. you should feel a noticeable increase in revs and the motor should be more responsive and hopefully return a better top speed.

[Tony Hart]

Fitted 15t sprocket yesterday but didn't get out on it. This had nothing to do with the howling wind and rain as real men ride in any weather - my wife said I had to come in to do the ironing

Away for the week now so will hopefully give it a go down to Wickstead on Sunday.

Thanks all for the input and will let you know how I get on. Warp speed or otherwise.

Tony

[Donnie]

When i had a 15 / 46 setup on my 175 and 22mm jetex with LI125 box it screamed in 4th, quickly changed to 16t on the front to make it much better. I'd suggest the same as previously mentioned personally.

[mainstand]

Talking of exhausts, for touring what's the general opinion of having a BGM clubman over a Taffspeed copy? To put on an engine with a 225, 28mm delly, GP200 box, 19/47 sprockets. Scoot pulls really well with the Taffy on but I'm thinking about a BGM clubby if it allows me to rev on a bit more..

Ta.

[Steve J]

Just one question - you say it's an iron 175 top end - does it have similar port sizes to the TV175 cylinder, or is it by any chance an overbored 150 barrel? (Or even worse, an overbored Li125.....)

[Tony Hart]

Hi Steve. I don't know about port size or template. I don't think it is a rebore but believe I got it from Camlam as a kit. When I fitted it the ports and piston married up as I turned the crank.

Tony

By that I mean that the piston crown was level with the bottom of the exhaust port at the bottom of its cycle but not sure of the transfer ports

[Steve J]

Hi Tony

I've just looked at the CamLam website - the iron 175 kits they currently list are Indian, so I would expect the port sizes to be at least the same sizes as GP150 ports, if not to Italian 175 sizes. It's good that the ports line up with the piston crown at BDC - not always the case with some alloy kits.....
It ought to be quicker than the 45mph on the flat you reported - was that a speedo figure or a true GPS reading? Most Lammy speedos are on the optimistic side, but there's always a chance you've got one that's reading less than your true speed, especially if it's an old one and the magnet's lost some of it's magnetism.

Steve

[Tony Hart]

Hi Steve. Unfortunately my 45mph is off a gps Just been for a quick run out with the gearing change and it responds better. As for top speed I will wait to comment until I see how it runs down to Wickstead in the morning.

[CHRIS in MARGATE]

Go for it !

[Tony Hart]

Warp speed was definitely not reached today. It pulled really well up to 40/45 mph at half throttle in fourth but then seemed to 'chug' as if short of fuel if I opened the throttle any more. I was in driving wind and rain as well and didn't want to push it. The best it managed in my 100 mile round trip was 51mph. I will up the main jet and fit the new exhaust I bought today at Wicksteed (Casa 42mm S2) and see how I get on.

[soullad]

Talking of exhausts, for touring what's the general opinion of having a BGM clubman over a Taffspeed copy? To put on an engine with a 225, 28mm delly, GP200 box, 19/47 sprockets. Scoot pulls really well with the Taffy on but I'm thinking about a BGM clubby if it allows me to rev on a bit more..

Ta.

Spoke to Ian Frankland about this at Cadwell last year. He said that Taffys used to sell shortened manifolds to help the pipes Rev on a little more. He said that 10 mm shorter allowed the pipe to rev on a further 4-500 rpm, obviously pushing the useable power that bit further up as well. Note, he did say it was a balance and that drastically shortening the overall
Length of the exhaust will initially make it a screamer then too far and it will kill most of the performance.
Might be cheaper to try and get hold of him and see if he's remade the shorter versions or get one modified? If you want the running boards back on and a standard looking pipe set up then the Bgm Clubman is a great choice. I fitted one to a mates IMola ( although somewhat altered) I'm really impressed, great all round pipe.

[Tony Hart]

I swapped the main jet to a 115 from a 112 and then moved to the other side of the bike as I decided to open the chaincase again due to paranoia with the strange noise on the way back from Wicksteed. The bloody tail pipe on the clubman had gone I assume that this could have been a factor in the noise and "chugging". (I still opened it to make sure ). The stud for the pipe was gone so I will need to look at that. It used to have a m7 stud in a timesert which has lasted at least 8000miles so I will try it with another m7 stud or possibly re- thread out to m8 if there is enough meat around the hole. I don't want to risk losing the rear pipe off my new casa exhaust.

With the larger main jet and new exhaust I am hoping to break the 45mph barrier. As usual it will have to wait until the weekend

[missing lynx]

did you open out the transfer ports in the casing to match the cylinder?

[Tony Hart]

I cleaned them up but the were a pretty good match to start with. I literally just smoothed them out.

[Tony Hart]

Gearing now back to a 15t sprocket with the 125 box, casa 42mm S2 exhaust fitted and main jet dropped to 110 in the SH1/20 carb. A brief run up the road got me to 52mph (GPS). More importantly when I change up to 4th I don't get the usual 'can't be arsed' response from the engine I will do the weekly commute to Portsmouth on it next weekend and see how it gets on .

[Tony Hart]

Rode down to Portsmouth tonight and sat nicely at fifty. Unfortunately scooter decided to shake itself to bits. Lost the cylinder head cowl bolts so spent an hour fitting one I borrowed from the flywheel cowl. That didn't last long so arrived in Portsmouth sounding like a rag and bone cart. On top of that the bracket for the tail pipe on the new exhaust snapped and I lost a casing stud that holds the exhaust main bracket. Four days to sort it out before I ride back up to Rutland. B****cks.

[MickYork]

Rode down to Portsmouth tonight and sat nicely at fifty. Unfortunately scooter decided to shake itself to bits. Lost the cylinder head cowl bolts so spent an hour fitting one I borrowed from the flywheel cowl. That didn't last long so arrived in Portsmouth sounding like a rag and bone cart. On top of that the bracket for the tail pipe on the new exhaust snapped and I lost a casing stud that holds the exhaust main bracket. Four days to sort it out before I ride back up to Rutland. B****cks.

Sounds like you've got it performing like a true Lambretta.......well done

[Wack]

Does the bike vibrate a lot? May have a twisted crank, robbing power and shaking the scoot to bits.

[Scooter Paul]

I agree with Wack'. This set up should run smoothly. I posted earlier that I've built several with 17x46 primary on a 125 box and they have all pulled strongly through all the gears. The whole vibration thing leads me to suspect something else wrong. It should not vibrate like this. Sorry if this is repetition.

Paul

[Tony Hart]

Hi Wack and Paul. I'm afraid that the crank is an innocent party on this occasion. I believe that the blame for my latest fiasco lies squarely with me. Cr*p attention to detail when I put it back together last time. There is no more than the usual vibration which on this bike is very slight. It now pulls great through all gears. It was pitch black when I drove down last night so couldn't really see my little GPS but the Speedo was sat at fifty and there was a bit more to go.

I have bought some more bolts for the cowl and tightened everything properly. A friend at work is going to weld the tail pipe bracket so that should be good to go. The Real pain is that when I took it to bits and rebuilt it tonight the exhaust bracket stud I thought I had lost has in fact snapped. I guess I will have to drill and re-tap it to m7. It will have to wait until I get back to Rutland at the weekend when I have more than an on the road tool kit.

Every journey is an adventure.