TV 175 conversion

[kevspeed]

After picking up some new/old stock top end parts for my TV2 last year,I decided to do a rebuild on the old girl,so barrel,piston,head,crankshaft were replaced,and she was back to the way Mr Innocent I intended.
The parts I removed were cleaned,oiled,and put to one side for spares in case of a calamity!
Anyway,Mrs kevspeed now has an Eibar series 2 for me to play with,and all is going well with the restoration as it was in excellent condition to start with.
To give it a bit more umph!,I have decided to use the top end parts that I removed from my TV2.
The barrel is actually from a TV3,and has been bored to 65mm for the old '200' conversion.
To keep the 'standard' look,a 20mm dellorto,jetted to TV3 spec with a slightly larger main jet has been fitted,and is breathing through a wide neck TV2 airbox,but the Eibar series 2 exhaust system has been retained,again for the 'standard' look.
Yesterdays road test was very disappointing,it goes like an Li125
I know the port design/timings on the TV3 were specifically designed to pull a much taller gearbox,and not to rev,but as I have retained the 150 gearbox I'm wondering could this be the problem?
As the gearbox is in perfect condition and selects flawlessly,I would rather fit a larger front sprocket to bring it up to near TV spec than replace.
Any helpful suggestions greatfully accepted

[johnnyXS]

does my head in even thinking about using TV175 engine parts

Can you give us a little more info Kev.
First of all do you think this is simply a question of lack of power from the engine ? or the wrong gear ratios ?
Does it have poor acceleration ....or poor top speed or both

The barrel is a standard TV175 series 3 that has been bored to 200 but retained standard 175 porting.
Which piston did you use , a standard series 3 TV175 ? or something else
Which crank have you used ?
Is the conrod a 107mm or a 117mm ?

If its a 200cc you should have plenty of power whatever gearing you've used so maybe it could be a timing issue ?

Tell us what your timing is and what jets you've used in the 20mm carb

[CHRIS in MARGATE]

Such a popular conversion in the day and went well. Have you used old 65 mm piston (175 - 200 conversion) and rings and if so are they worn. New rings perhaps?
Might have to get 66mm and file to suit.
But I'm going for the exhaust box.
150 Gearing should make it feel even livelier.

[kevspeed]

does my head in even thinking about using TV175 engine parts

Can you give us a little more info Kev.
First of all do you think this is simply a question of lack of power from the engine ? or the wrong gear ratios ?
Does it have poor acceleration ....or poor top speed or both

The barrel is a standard TV175 series 3 that has been bored to 200 but retained standard 175 porting.
Which piston did you use , a standard series 3 TV175 ? or something else
Which crank have you used ?
Is the conrod a 107mm or a 117mm ?

If its a 200cc you should have plenty of power whatever gearing you've used so maybe it could be a timing issue ?

Tell us what your timing is and what jets you've used in the 20mm carb

Basically lack of everything,just no real 'go' as you would expect from a TV175.
The whole top end set up/crank came out of my tv2,which was an easy starter,smooth,55mph all day,top out at just over 60mph.
The barrel had been bored to suit the '200cc' conversion (65mm piston) and the correct new/old stock piston is fitted,done around 5000 miles,new rings fitted about 2000 ago,both ring gap and piston/bore clearance well within tolerance,(i picked a couple of these up many years ago and have the next two oversizes if required).
The crankshaft assembly is series 3 TV175 (117mm rod),timing set at 17 degrees by strobe,and the jetting in the 20mm Dellorto is number 1 slide,number 2 atomizer,52 pilot (2 bigger than standard),50 choke,and a 110 main jet (4 bigger than the standard 106).
The exhaust system has been cleaned out and no blockages are evident,but i am going to try another as part of the process of elimination.

[johnnyXS]

well there doesn't appear to be anything particularly wrong with that setup that stands out.

I would suggest that you try 19 degrees timing though which is what I run my series 3 LIS150 at .
As you say it should feel pretty quick with a 200cc engine and 150 gears

What happens when you hold a steady throttle at say 40mph . Does the engine surge at all ? or does it cough or splutter or anything ?
Does it ever bog ? what colour are the plugs after a good run ?

[kevspeed]

Going to have another crack at it today,process of elimination,re-check everything.

[Adam_Winstone]

Gearing will not be the issue. As already stated, the LI150 box should make it feel even peppier than standard, and would only become a limiting factor (perhaps) if you were finding that it screams away in 4th but then can scream no higher (at about 60+mph), which doesn't sound like it is your issue. Remember LI150 = 5.2:1, which is the same as a GP200.

Jetting is most likely to be one of your problems, with you starting too rich and stopping the motor from being able to cleanly get to where the power is. The TV175's 50 pilot was/is commonly too bigm which is why Innocenti dropped to 48 and then to 45 for their subsequent 200cc models. You might find that a 48 is still too big, let alone a 52. With the SIII having a comparatively free flowing intake and an exhaust that revs far higher than the SI/SII and early SIII exhausts. TV200, SX150, all of the GPs have the non-mushroom baffle pipe and this makes a really (surprisingly!) big difference to how a standard motor will rev / breathe. Going rich on jetting can further restrict an early hybrid motor from revving! Then consider your main and the fact that a TV200 has a smaller main (108) and an SX200 smaller again (103), along with the same 175/200 atomiser #2 and you're again running rich. NB: You may find that a 110/112 main is actually fine with an iron 175 and standard porting/carb if running the later free-flowing SIII pipe.

In light of what we know so far (excluding massive ring gaps, wear, very low compression or huge squish clearance, etc.) then I'd suggest that your jetting is too rich for your motor's ability to breathe it in and through. Exhaust will make a big difference to this and jetting doesn't want to be much (perhaps any) richer than a standard 175/200. What you will want to do is to keep the motor cool by retarding the ignition timing (required for today's hotter burning fuels... somewhere between 19 and 21 dbtdc), rather than thinking that it is the extra fuel that will keep it cool. As it stands, I am leaning towards it being the extra fuel that is stopping it from clearing and performing as it should (combined with the pipe).

Good luck with it.

Adam

[johnnyXS]

Adam ..kev says that his current timing is set at 17 degrees , so he doesn't want to retard it ..... he needs to advance it to 19 degrees
I always prefer to use a timing degree wheel to check the static timing initially at least . I don't trust timing lights on a 2x stoke because its difficult to know what rpm the engine is doing

If his mixture was too rich I would expect it to show by the engine bogging , being difficult to start and wet black spark plug etc which is why I asked about the throttle response.
Interesting that you mentioned squish . Thats a definite possibility as is incorrect porting .I was quite surprised how much difference a few thou squish can make to the power as shown in that Scootering article old school porting .

Talking about jetting.... I see that the TV200 used a 20mm carb with a 5889-2 Atomiser (1.75mm dia bore) and a 48 pilot and 108 Main jet .
I think that a 200cc needs a 22mm carb .The larger bore should flow more fuel /air but Kev wants to keep the scoot looking original so that rules that out

[Adam_Winstone]

Missed that... yep, 17 is probably less than ideal on a very standard ported motor with an original TV175 head (compression is probably fine with 19 degrees ignition advance).

20 VS. 22mm... if you every ride a standard SX or TV200 then the standard configuration rides very well, which is part down to the good torque, small carb and long (high) gearing combo. It is not a coincidence that Innocenti shortened the gearing at the same time they fitted a bigger carb, which allowed the motor to use the extra revs that it resulted in. As such, the 20mm will be perfectly big enough on the standard porting that I understand this barrel has (or did I miss that too , typical me!).

I use big carbs all the time, on different spec motors, so I'm in no way anti big carbs, but I don't think that the 20mm needs replacing for this motor's spec'. Indeed, having had a number of mild tune iron 175s on 5.2 gearing, with later spec standard SIII pipe and 20mm carb, they can perform and rev surprisingly well.

Adam

PS - A pal of mine asked me to set his ignition timing on his iron 150 (might have had a 175 conversion... I can't remember) before the South Downs run this year. His compression was very low (but not leaking) and the barrel was totally standard porting so I set that to 19 dbtdc (anything ported would have had me set it to 17) and he did the run 2 up and without issue. Prior to me setting the timing it had nipped up a number of times.

[johnnyXS]

thats very interesting Adam.

i read somewhere recently that straight 150cc to 200cc conversions are performing extremly well in racing so a small block 200cc must have plenty of potential .
Mark Broadhurst I think it was that said in his experience larger bore carbs often performed worse .

My original SH1/18 carb was damaged so I bought a new 22mm Jetex. At first it ran terrible and I had to make a lot of adjustments to the float pivot and jetting before I suddenly hit on what seems to be a perfect combo for the standard LiS150 special which is 45 pilot, 5889-2 Atomiser and 106 Main running at 19 degrees static. I have never tried a 18mm carb on it so I cannot compare unfortunately .

I really think it pays to experiment though ...as even a change from 108 main to 106 Main jet transformed the performance and made it easier to start and added 8-10Mph to the top end on mine

[Adam_Winstone]

^... interestingly, I've typically found that the best combo for iron 175s with 22mm carbs (Jetex or Dellorto) is to ditch the #2 atomiser and to fit the leaner #1 or #4 atomiser with a much larger main jet (118-125), otherwise the rich atomiser gets it to bog out too early (too much too soon). Incidentally, this is also quite a common change when getting a standard SIL 200 IV dynoed as they too tend to bog out at not much more than 50mph. The leaner atomiser allows them to progress past the otherwise rich mid range and get to the higher revs and better power that they should be reaching, then the larger main ensures that they get the fuel that they require at 3/4 and above.

If your combo works well on your motor then do stick with it as every motor is different. I've run the #4 atomiser with a 138 main jet on an iron 225 with RS clubman and reamed 25mm Dellorto, with that bike doing thousands of Euro miles at major road speeds, which I had to change to in the middle of France as I simply couldn't balance mid and top with the #2 atomiser.

Horses for courses and every motor differs but I was not surprised when a pal of mine came back from a well respected dyno operator / Lambretta tuner with a #4 and 125 (might have been 123) fitted to his factory SIL IV 200. Having this has transformed the ride and it no longer bogs out at 50-55mph, rather rides clean through to over 60 and considerably more.

Adam

[EddieStone]

^... interestingly, I've typically found that the best combo for iron 175s with 22mm carbs (Jetex or Dellorto) is to ditch the #2 atomiser and to fit the leaner #1 or #4 atomiser with a much larger main jet (118-125), otherwise the rich atomiser gets it to bog out too early (too much too soon). Incidentally, this is also quite a common change when getting a standard SIL 200 IV dynoed as they too tend to bog out at not much more than 50mph. The leaner atomiser allows them to progress past the otherwise rich mid range and get to the higher revs and better power that they should be reaching, then the larger main ensures that they get the fuel that they require at 3/4 and above.

If your combo works well on your motor then do stick with it as every motor is different. I've run the #4 atomiser with a 138 main jet on an iron 225 with RS clubman and reamed 25mm Dellorto, with that bike doing thousands of Euro miles at major road speeds, which I had to change to in the middle of France as I simply couldn't balance mid and top with the #2 atomiser.

Horses for courses and every motor differs but I was not surprised when a pal of mine came back from a well respected dyno operator / Lambretta tuner with a #4 and 125 (might have been 123) fitted to his factory SIL IV 200. Having this has transformed the ride and it no longer bogs out at 50-55mph, rather rides clean through to over 60 and considerably more.

Adam

I'll second this.

[johnnyXS]

^... interestingly, I've typically found that the best combo for iron 175s with 22mm carbs (Jetex or Dellorto) is to ditch the #2 atomiser and to fit the leaner #1 or #4 atomiser with a much larger main jet (118-125), otherwise the rich atomiser gets it to bog out too early (too much too soon).

Adam

thats an odd result ?

The 5899-1 has a 1.5mm bore... whereas the 5899-2 has a larger 1.75mm bore otherwise they are identical in all respects except the lowest row of holes, which are 1.0 mm Dia on the 5899-1 and 0.9mm Dia on the 5899-2 .
Such a minute difference of 0.005mm is negligable but the difference in bore is quite large and would make quite a difference to mid and top end flo rate . I find it hard to believe that a 5899-1 Atomiser could flow sufficient fuel for a 200cc engine through a 1.5mm Atomiser bore whatever size Main jet is fitted.
The 5899-1 Atomiser is only recommended for the Li 125 & Li150cc series 3 engines. but I'll have to try your suggestion on my 150 Special )

The 5899-4 Atomiser also has a 1.75mm Dia bore the same as a 5899-2
The lower and middle row of holes are 0.80mm, ( virtually the same as both the 5899-1 & 5899-2 ,)the big difference is the top row of holes which are huge at 1.2mm which will give a big shot of fuel from the pilot jet to improve initial throttle response when the throttle is snapped wide open otherwise the suddenly wide open venturi would lower the vacuum momentarily and insufficient fuel would be drawn from the main jet.This would result in bogging off idle symptoms.

[kevspeed]

Sorted..........Note to self..........Pay more attention!
Re-checked everything,(my timing was actually set at 19,and not 17 as i thought
Anyway,the problem looks to have been the exhaust box all along (as Chris and Adam mentioned).
Initially the tailpipe and stub were poked through successfully,then cleaned out with a portion of large diameter cable in a drill,so no blockage was suspected there.
As this is an Eibar exhaust box,i assumed that it would be the same as the Italian box,but no!
Instead of the internal baffle at the end of the downpipe stub,there is a 'dead end'. The only way any gases can get into the box is via a few small holes in the sides of the pipe,so i armed myself with a length of inch diameter solid bar and battered the dead end off ,it worked a treat,the exhaust note is a bit louder,but not too much,just a tad quieter than a 42 clubman.
A few trips round the block and she goes like you would expect ,although due to clutch slip the side will have to come off again,so i will be up gearing with a larger front sprocket ( a 16 should give me 4.9,so not far off TV spec top).
The jetting will be checked via plug chops once its on the road properly,i just opted for the slightly larger sizes due to using the bigger necked TV2 airbox.
Anyway,thanks all for the input,every day there is something to learn!

[johnnyXS]

great result Kev and good to have a solution for future searches that find this thread.
Its so easy to take things like this for granted .'
Anyway we all had a nice chat about stuff whilst you were away lol