Re: Fiero/FieroF2/FieroFx

Yeah,it's nice to ride in rains. Yes ,you are right,to fit the 200 head on our 180 bores,we have to mill the head in order to increase the compression.Along with that we have to modify the Stock RTR 180 piston to match it. The thing is, the lathe guy who did the job is quite good,he had already done these modifications to many rtr/fieros,in fact he has very high regard for TVS bores and heads,such that he has even installed RTR 200 bore and it's 4 valve head onto a hero impulse. This lathe is quite famous for it's work and i guess he knows a thing or two about bores and hence there must be something about this TVS platform. The lathe in question is ZEN. So i wasn't the first to get this modifications done,in fact there were already many fieros running with this modifications and it as @abhilash_abhi who spotted this mod for the first time.
Coming to the oil cooler,yes tvs has changed the oil routing to the head ,as well as the oil cooler outlet.Oil cooler outlet now comes to the oil filter area and from there the oil goes to the head internally through the bore.You might see this being suggested as a modification alternative to my current set-up,as it was suggested by now late Mr Srinivas formerly of TVS R&D and Mr Venugopal.So tvs has taken the same route for the RTR 200.

The important thing here is that TVS has left a provision in the head for the oil line to head.That is ,they have been good enough to leave this provision so that older models of rtr/fieros can convert and fit the new 4 valve head. So we should be thankful to TVS for leaving this provision in the head,that's why this modification becomes nothing more than a bolt-on job.
The oil cooler is still there in the same manner on my bike as it was before and we need not change it either.

The other way to install the 200 head onto 180 bore is by milling the bore itself to increase the compression.But what we found was that there's zero deck clearance in RTR 180 bores. Tvs doesn't leave clearance between the piston top with the height of the bore.That's so because they want to maintain good compression like it must be the case with all other indian bikes as well.

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These are some of the pictures.The impulse belongs to the lathe owner and the fiero is mine.

Re: Fiero/FieroF2/FieroFx

Firstly, nice pix, Gixxer bro. Thanks for sharing. I have a better understanding of the works carried out. Okay, so you milled the head. Even 0.5 mm of milling it would have raised the compression ratio of your set up. Your previous comp ratio would have been around 9.5:1 as I'm on the same too I assume. Logically, you have milled or shaved maybe more than 1 mm to match the bore? Kindly confirm. Also, that's the reason you had to modify the piston. Was it because valve recesses needed to be cut into the crown? Four of them in rtr 200 head's case. The valves when open would be very close to the piston I feel, if no recesses were there. Also, you're right about the deck clearance of the bore. So, you are once again on high comp set up. It might be more than 10:1 ratio. Pls correct me if I'm wrong. Have you retarded the timing to be on the safe side to avoid knocking. I'm guessing with this set up, you'll enjoy high octane petrol.

Your lathe operator friend at Zen is extremely good. I like that big bore project of his impulse. Seeing that an impulse also has 57.8 mm stroke just like our fieros and rtr 180 / 200, his set up will be 200 cc as per my calc.

Your projects as always are very enlightenimg and inspiring. So if your run in is complete, you might be enjoying crazy triple digit speeds as 4 valves are always better for top end

Re: Fiero/FieroF2/FieroFx

The compression is high,i can feel it when kicking and bringing it to tdc. The thing i have noticed about the 4 valve set-up is that it is easy to kick start from tdc. That is, the entire valve train is now smaller than that of the 2 valve head,so it's very easy to move,which is the reason why 4 valve heads along with better breathability mean more revs and more power higher up the rev range. The rocker arms are small and lighter by a huge margin in comparison to that of the earlier 2 valve ones,Earlier i was expecting a hard kick start procedure when i knew the compression will be high,but i was pleasantly surprised as to how easy it is to move the valvetrain from tdc.

The ignition timing is still set at the advanced curve only,without a TPS that is.There are no knocking problems either.

About the milling,i am sure it was within 1 mm. The thing is i left it to the lathe to do the job and all i told him was to ensure that higher compression is there.The piston was modified for the 4 valve head as you said,then he has also ensured that this modification gives more compression. I will be using the same milled head later when i will switch over to 200 bore and yes it will mean more compression than a stock rtr 200.That's what i wanted anyway.

The jetting is still going on,i got a main jet drilled at a nearby lathe on saturday,it was that of the zma and now it has been drilled to 1.4mm.The new plug is showing that jetting is ok,but it's still a bit on the leaner side.So you can imagine what the change has been with regard to breathing ability of the head.The bend pipe is working well with this head and hence the need for bigger main jets.In mikuni jets with a 1.4mm hole ,it would be numbered at 130.That 130 is flow rate that is.So,yes still in search of main jets and jetting is now stable,but still not done yet i think.

About the running-in, it's not needed as none of the parts from the cylinder has been changed from what it was. You can still see the carbon on the piston top,the mech hasn't cleaned it totally.The rings and piston are same.So is the bore.The cylinder ,piston,rings and the rtr 2 valve head all were fine and didn't need any work. I got this modification done just for the sake of it and not because of the previous set-up needed any engine work. I got her FC done,so this is kinda like my gift to her . As a side note,i have been using shell oils mostly and i was surprised as to how clean and new looking the pistons sides were and the RTR 2 valve head looked spanking new!So most probably shell oils are quite good as claimed and frequent oil changes does work.

Re: Fiero/FieroF2/FieroFx

Oh cool. Nice pix again. Yes, I see what you mean by the valve train being smaller. They do look light. This will make your engine very rev-happy besides the advantage of over square block too. But you are right in planning for a 200 cc bore. This head set up is just dying to be matched with a 200 cc piston. And bcuz of your milled head, you will enjoy high comp too. So bcuz of that you won't feel the loss at initial.
In fact, I think I can see in your pix, that you hsve polished the ports slightly too. Or was the carbon taken off freshly by the lathe operator?

Have you retained original chain sprocket ratio with this engine set up? It might power wheelie in the second gear with original chain sprocket ratio. You might have retained your 15T GB sprocket I guess.

So that Himalayan jet didn't work out? What are your thoughts on the keihin carb that TVS has plonked with the rtr 200? If its inlet matches our fiero/rtr air box hose and manifold, then you could use it without stress. Or is the bs29 you are using slightly better for torque in mids?

Yes, there is no need for running in. I think you need to drag against a rtr 200 now and leave it behind :P Congrats on the FC test. You just gave new pife to your bike. Cheers. And where is Abhi? From what you said, he is still eyeing Fieros (stock or modded) even though he isn't riding one now :P Drop in a hi to him from my side. I miss the leg-pulling banter

Re: Fiero/FieroF2/FieroFx

@abhilashabhi12 he was involved in a head on collision with guess what? another p220! no one knows as to what or who he was eyeing That lead to him eyeing the modified fiero and from there it began. Him and @Ramankr77 who is another dude like us, started this interest.

The sprockets are 14/39, which is from a while now.Yeah going back to 13/39 will mean some serious acceleration for sure.

Still waiting to get my hands on himalayan jet and then to drill it further.I don't know whether the keihin carb is also a 29mm one or 30 ,either way, there's no issue in fitting our bs29 carb.Keihin carbs cost a bomb and their parts are costly too,so i don't think i will be taking that route for now.Besides i already have a spare bs29 with me. The intake manifold is that of the rtr 200.Carb jetting is almost complete ,let's see how long it takes.As the main jets are easily available at bajaj,we'd have to drill them ofcourse,so it should not be a problem.Besides jetting is never a quick, or an easy job when the set up in question isn't stock.The mikuni 29mm CV carb is good enough to make a Suzuki FX150R hit genuine 153 kmph,so this carb is more than enough for us ,i guess.

The reason i didn't go for the 200 bore of rtr ,is because it will need crank to be opened in order to fit it's connecting rod ,but since my bike's crank has never been opened till date,i didn't want to do that now either.Besides the 180 bore is still good ,so i wanted to run the same with 4 valve head.But yeah,i want to run a higher compression than stock with the 200 bore,so i went for milling the head mod.
The ports are stock. That's how the head was.

Re: Fiero/FieroF2/FieroFx


Oh, okay. So, the rtr 200 bore is not mere plug and play? I thought it would be a straight fit. Has the company put another con rod with the crank? The stroke is shown the same as on paper. Does the 200 piston skirt touch the con rod during operation? Those stock ports look superb Knowing you, I thought they were modded as well

Bro, so the rtr clutch handles the extra power? I'm feeling like putting the rtr clutch on my fiero too now. Besides the clutch cover, I need the entire clutch basket assy right? Do I need idler gear and gear pump for oil too? Rtr gear pump sends more oil per rotation than fiero's. What else do I need to change? Kindly advise.

Hehe. So abhi is riding his p220 hard I see. Judging by your emoticons, I'm sure he's fine But is he heading back to fieros again now? :P I'm sure you taunted him to get one again.

Re: Fiero/FieroF2/FieroFx

Tvs, as far as i know,has increased the cylinder height for the rtr 200,but as the stroke length is still the same,so they have increased the connecting rod length.Their aim was just that i guess.

Yeah,RTR clutch can handle the power.For this you will have to change the entire clutch bell assembly,except the primary drive and ofcourse the clutch cover. Rtr from hyper edge series onwards have increased capacity oil pump ,yes,but that's only because they want to run thinner oil than earlier models,that's all.With thinner oils,engine life will go down drastically with our bikes. Mr Srinivas himself had recommended the use of w50 oils on our bikes,he was in TVS R&D,so he must know something.The least we can do is run them with w40 weight. Other than that,there's no need to change oil pump gear ,or any other gear for that matter.But you would have to drill a D shaped hole into the input shaft for the clutch release button.

Re: Fiero/FieroF2/FieroFx


Oh okay. So they increased the con rod throw but retained the same stroke as before.

Do you have any pix of the rtr clutch conversion? If i remember correctly I had heard of the older rtrs having more spring rating too. The newer models have shorter length springs. Had seen a pic somewhere of that. It would be interesting to see how that D shaped hole looks like exactly. I thought it would be plug and play Is there another way you have tried without drilling?
Would it help if I PMed you here?

You're right about w50 oils. It felt necessary in 150 set-up itself. Especially when high compression is there, it will help with better heat dissipation too. Plus your oil cooler is there too. So I'm sure temps are within control

Re: Fiero/FieroF2/FieroFx

No i don't have that particular picture as i haven't gotten it done.But here's a couple just for reference,though they don't show the D shaped hole.

The first is that of the rtr 160/180 and you can make out the female part of the clutch release button within the bearing at the center.This will be the one which will be partly inside the input shaft's D shaped hole.

There are 2 ways this modification can be done.

1. Modify the clutch release button assembly itself and make it work without drilling the D shaped hole into the input shaft.We did this first and it works perfectly fine too.

2. Second method is to go to the nearest honda/hero showroom and buy unicorn's clutch release button and put it. Simple! That's what my bike is using right now.

Re: Fiero/FieroF2/FieroFx




I'm not saying this is a bad mod, but I just had a doubt that struck me just now. As you are the best person to bounce it off, do be patient with me Is the rtr clutch (entire unit) slightly heavier than the fiero clutch? Have you felt that the weight is more when you handled both assys during the removal and fitment? If it is, does it affect the balance of anything in any way, like say, the crank itself? Does the magnet on the other side have to be heavier too then? So that the balance is maintained? I hope I haven't confused you


Otherwise, as you said, it seems perfect and necessary for a bumped-up fiero. The extra power needs a new robust clutch like the one you have and shown.


So, over time, as you have ridden both versions of this mod for quite some time, which one do you recommend? As in, in terms of reliability and performance, are both similar?

Re: Fiero/FieroF2/FieroFx

RTR unit is more robust, with whole lot stronger springs,other than that there's no difference in weight as such between the two.Now,talking about crank going out of balance,as you know, the clutch is fitted on the input shaft,so no issues as such.

Fiero needs new clutch springs every clutch change,besides the 200 buck cheap chinese ones never last as long as the original japanese FCC ones the fieros came with,so definitely RTR clutch is better by far.
There are many fieros running with RTR clutch from a long time now.They all are running with RTR clutch release button.That is with their input shafts drilled to fit the clutch release button and they are as reliable as stock RTR. But,there are only 2 bikes,including mine,which are running with our kinda modification and so far there are no issues what so ever. The mechanism used by TVS is quite uniqe for india. In the sense that as far as i know,no other bike runs with that kinda clutch release system. So i am sure there must be a good reason as to why TVS adopted that system.The RTR mechanism will definitely ensure longer life for the release bearing,compared to my modified clutch system,maybe with even more benefits.But,then i modified it to work, as it does on the unicorn,which is a honda.So how bad can it be?

Re: Fiero/FieroF2/FieroFx




Yes, these HCM ones seem to wear off a bit faster with 180 mod. They are fine for 150. I didn't change them as often at that time. But now, after overboring, I have felt they can't keep up that well. They don't slip, but they tend to lose bite eventually. I tightened the springs and they seemed fine for a few thousand kms with the extra steel plate mod. But I have tried the RTR clutch on the apache 160s and 180s and they give a good 'grabby' feel. I'm sure they will last longer as they are designed for more power. The fiero ones wear out fast because of the extra power. So, the next time I change my plates, I will definitely be tempted for this RTR mod conversion. I have always ridden on half-clutch setting as I learned that on 2-stroke bikes growing up and that setting is the best for me


Thanks really so much as always for the info Your confirmation about the weight of the assy is reassuring. If only there was a pic of the drilled section, but that's okay. I'll try and figure it out at the time. Or I will look into your modified set-up with unicorn donor parts. That seems advantageous because there is no drilling involved. Although, the rtr set-up you mentioned is also robust. And you're right, the Unicorn clutch by Honda is not bad at all. So, no worries there.

Re: Fiero/FieroF2/FieroFx

Guyz i am working on my fireo f2 to make it a cafe racer.
Needed some assistance regarding the same.
Just wanted to know , Is it possible to fit CBR 250R Swingarm in fiero f2 ?

Re: Fiero/FieroF2/FieroFx

Here are some pics of the work i am doing

Re: Fiero/FieroF2/FieroFx


Welcome to the forum.
You've picked a nice chassis and engine platform for your cafe racer project.
If you search in the past pages, you'll find detailed info about compatible swingarms.
What else have you planned for your bike?