Before anything - as have earlier mentioned - if you want to read the best article ever on building a dragbike, read this. After that you wont feel like reading whats left out here. So having setup a junction out here, let me move on to our stuff.
The story begins around one year back. We guys are back after a drag and i see Tom brooding around with a thoughtful expression on his face. So whats up. Tom blurts it out - motor, im sick of watching bikes ripping up and down the strip. Why dont we build our own drag bike and kick some ass.
Well idea is appealing. Soon we sit down for some serious planning. First step is decided upon - we need to find a broken down RD going cheap; yes, a scrap bike for a low cost. And then start working on it and come up with a full blown dragster.
The concept of a Junk bike enters the picture because of the enormous differences between a normal streetlegal RD and a drag RD. Just think about it.
The engine - A dragster's engine is a fullblown heavily modified monster without a care in the world about fuel conception or life in terms of miles.
The carbs - Dragsters go in action with heavy duty carbs like 34 or 36mm.
Pipes - Poles apart from the road-friendly straight pipes of a street RD, a drag machine needs specially designed Expansion Chambers for providing that boost. Least bothered about concepts like noise pollution. Hear a drag RD on song and you would wish you didnt have ears.
Ignition - A stock ignition wont work on a drag bike. You need a specially built custom racing CDI.
Other items like Mudguards, headlights, switches, kicker etc - For a drag RD, these are totally unnecessary masses coming for a free ride and eating away on acceleration. Dont need any of them.
In short the only common stuff turns out to be the frame/tyres. And at extreme levels, this doesnt hold good, too.
So we have to search out a scrapbike going cheap.
Easier said than done - suffice it to say that we spent around 8 months hunting for our dream scrap bike going hell cheap. No luck. We juggled with different ideas. one was to use Toms bike and convert it. Wouldnt work since tom plans to sell his RD for the money to pump into our drag project. Another was to use mine - again problems, since it was my daily bike and i just couldnt dream of living without an everyday roadrunning legal RD. We used to call my bike 'Uncle' cos of its age - it was a 1987 model. So dont get confused by a train of references to Uncle.
Uncle as it was on 22 June 2003.
At this stage something (UN)fortunate happened. I lost my bikes papers - so effectively i was stuck up with a street-illegal RD which i could neither sell nor use everyday. Any more roadrunning meant a stream of hefty cop fines.
But yes everything clicked. I needed a daily bike. And tom wanted to sell his bike. So i decided to buy Toms bike so he gets money to pump. And convert my bike into the dragster. Since it was good for nothing else anymore.
So it all began to happen and one fine friday evening loaded with TGIF beers i handed over the cash to tom and went home with his bike.
First step accomplished. We have a base bike to start working.
Second step was to start working - This present few confusions as there was nobody around within a radius of thousand kms who could do up a good drag RD except Ron.
Our basic idea stemmed from the fact that most of the ported and piped RDs out there were running poor times like 14.x. We figured that just fitting Uncle with some good pipes from Ron would pull us straight into that land. At least close to it.
We call up Ron; Yes he is fine with the idea and agrees to make us the pipes. But he needs to look into the engine first and check the ports. Especially since he knows that Uncle is already ported - though mildly - by my mechanic. No prizes for guessing that the mech would have done a horrible job. He asks us to bring the bike over and instructs us to bring the Bit for lifting the head. Same day i make a run to JC road and buy two 17 size Taparia bits at 45 rs each. Plus the rod for another 50. is 17.
Here is a pic of the pipes which Ron makes :
pic : courtesy - ron, rddreams
Soon we take Uncle to Rons place. The first 20 minutes flashes by as the bits and our hands go to work and the heads come up.
Yeah the ports are a bit butchered; Funny thing is the mech has more or less left alone the exhaust port roofs - hardly 1mm has taken off. He has really gone violent with the bottom of the exhaust port, diggin a big 'pit' into what was a smooth curve. And Ron tells us that the bottom of the port has no effect and we are left wondering why the mech went hard on that.
Anyway the fact becomes clear - Just running Chambers on those ports is not a good idea. We decide for a level of porting and then to run chambers on top of that.
courtesy: ron, rddreamss
But its goodnews since the mech has left alone what we needed - the Roof. We observe that there are problems with Blowdown - The Transfers were opening up too soon after the exhaust. Resulting in exhaust gases moving into the transfers instead of diving out of the exhaust.
All in all nothing irreversible has been done already. The plan is to go ahead in stages. Three in total. First stage is decided upon - Something we have begun to call the 'danny' specs. A spec between the LT and the HT as far as port sizes are concerned - but rpms grow all the way till 8500. The torque peaks at 7500rpm and the BHP at 8000. second stage is something we call 'killer' specs. Yes in name of the Madman killer which i have mentioned in another page. This is something more than the US specs. A lil above US spec porting. Third is an all-out full-blown dragster. The third stage is a totally different ballgame. And one look at the liner convinces Ron that we would need new hard liners to think abt the Third stage. And second stage itself would mean a complete crank work. But right now we are moving into the First stage and the crank is supposed to hold fine. Since only one conrod shows any signs of unsteadiness.
So within two hours the plans are finalized. Danny specs it is for First stage.
But we need Heads. The existing ones are sleeved. I ring up my mech and find that he has two heads with him, unsleeved he claims. Asking price is 950rs for the pair. He agrees for an exchange deal at 500rs. And soon we walk out of Rons place, agreeing to bring him the heads within two days. Provided we bring the heads within the next two days, Ron agrees to finish his work within a further two days so that we can test the bike over the next weekend. The idea is to get a measure of performance without disturbing anything else. Find how the bike moves with the new porting, the old stock pipes and the local CDI which the bike carries now. By that time, the chambers would be done; Bolt them on and see what difference it makes; And last remove the CDI and fit in a better one and check once more. Then take it on to the dragstrip. Stage one.
Soon its twilight and 22 June Sunday 2003 creeps to a close. After gulping down some Smirnoff shots, i flop down to dreams of testing the ported bike over the coming weekend.
The plans for the first stage are pretty simple; Thanks to the speed gun, we have observed most ported&piped RDs finishing at around 140kmphr plus. And the times work out to around 14 - 15 seconds. The aim is basically the same; A terminal speed of 140 kmphr plus. Hoping to get under 15 seconds. In effect something that would cross 140kmphr in under 15 seconds. You might understand the scene better if you take a look at the finishing speeds from the last drag at the Jakku airstrip.
Uncle in stock condition used to have a terminal whack of around 112 kmphr; After the mech's porting it got to around 120 kmphr. With the new porting we expect this to reach past 130kmphr. Say 133 kmphr. Now plug on the Chambers, a better CDI (its running a local one now) and there is a good chance of crossing 140 at the end of 400 meters. Guess the final topspeed would have to be around 150-160kmphr.
The stock Uncle used to be very quick; ie, while it was on 4th oversize pistons. The day i rebored and switched over to 5th oversize, the power past 5k rpms disappeared without a trace. The lowend increased noticeably, yes. But the moment 5k rpms loomed, it ran into a brick wall. Used to revv past 5k, yes; But pure overrev with no useful torque. In effect 100 in 6th gear appeared quick - rest of the action was forgettable. Ron explained to us how the blowdown issues began to affect seriously once the CC was increased by the rebore.
So next day i get the exchange deal done and we go over to Rons place; Only to find that one head is not good - its sleeved, too. My mistake. So now its thursday and we need to give that head back to the mech and procure another one.
1 - 51.68 kmphr
2 - 74.88
3 - 101
4 - 127
5 - 149.7
6 - 169.5
The quarter mile time for the US spec RD is around 14.3. At around 150kmphr.
Now assume somebody dragging this bike. Assume he pushes the bike to the redline - 8500rpm - in each gear.
Say he launches at 4k rpm. And pushes in first gear to 8500 rpm - which is a speed of 51.68 kmphr - and then shifts to 2nd. So the revvs drop to 5.9k rpm. Because by the gear ratios, thats the rpm in second gear, for a speed of 51.68 kmphr. Similarly working out for all gears, the tacho movement for the whole run works out as :
1st - 4k to 8.5k
2nd - 5.9k to 8.5k
3rd - 6.3k to 8.5k
4th - 6.7k to 8.5k
5th - 7.2k to 8.5k
6th - 7.5k to 8.5k
You can discount the 6th gear as the US spec RD hits 400 meters when it just redlines in 5th.
The data that evolves from this calculation is that - any power below 5.9k rpm is useful only for the launch; ie only in first gear. And the rpm range that is hit throughout in all gears is 7200 - 8500 rpm.
As per above, the danny-spec seems to fit in prefectly. Torque peaks at 7500 and power at 8500. So all through the gears the torque peak is used. Only worry right now might be an over-abundance of torque at low rpms; Leading to a nasty wheelie eating up a precious half second or one.
Anyway right now the choice looks fine; Throw Chambers on top and we should get something thats quick, real quick to 8500 rpm in each gear. And it would be a very pleasant surprise if we end up finishing in 6th gear. Which i doubt, though.
Downside - yes there is one. Due to financial reasons no way to make a separate Chamber for each stage. So the Chamber has to be designed to take care of the second and third stages - something that kicks in at rpms above 8000. This obviously is not a good combination with the First stage danny-spec; But thats something we have to live with, as far as Stage 1 is concerned..
Ok so its saturday soon. And the whole day is spent roaming around in the local Junkyard and the street where you get Auto spares. I come home with an RD head (400rs) a 1mm thick 1 X 2 foot gasket sheet and a 1 X 1/2 foot and 1mm thick copper sheet. All in all some 250rs.
And back to rons place the same day, only to hear that both the gasket sheet and copper one are too thick; Not that they are useless. But to put it short, i need to go back and get thinner ones. I also carry back home a diagram of a TZ gasket with me, on the gasket sheet. Which i need to cut and use for more cuts from the new thinner material which i hope to buy on monday. But the head is fine; Its not sleeved and will work. So head-hunting is over and the pair will travel to the lathe soon, for shaving etc. Then Ron informs us that he is finished with the porting work.
Bad but i cant post the pics of the finished ports out here. Ron will skin me alive if i do that. So work your imagination when i tell you that the finished stuff is nothing like the savagery which you saw up above. Its a beautiful job, neat clean and precise.
Not much action on sunday, 29th june. except for one hour spent on cutting out the TZ gasket. Managed to cut open one finger big time. Cant work anymore with a bleeding finger so i throw the half-cut material into the shelf.
Back to office on monday and waiting for a chance to get off to SJP road and get those thinner sheets.
One strange thing i noticed. The more im getting involved into this project, the less i feel like drinking. Earlier, evenings seemed to fill up the brain with a strange vacuum which used to suck in tons of depression. Now there is no vacuum but a longlost feeling of a strange anticipation. The mind seems to be back in love with the present and the future. Suddenly, after a bloody long time, the past looks boring, dull and colourless.
Anyway back to monday afternoon. Back from SP road with a 0.25mm thick 1X2 foot copper sheet and a 1mm thick 1X2 gasket sheet. And a 100gm tube of 3-bond. 285rs. If you are in bangalore and if you need copper or gasket sheets, then go straight to SP road. Pretty near JC road.
Hopefully these materials should be ok and now all set for Ron's call telling us the heads are back from lathe. Im only worried abt the copper sheet which looks a bit too thin. But then the 0.5 one looks a bit too thick. So once the call comes, we just need to go over and put the engine together. Meanwhile i have a little more work left today evening - i need to cut some gaskets. Not fingers this time, i hope.
And the link gives me these formulas :
ET = ((Weight / HP)^.333) * 5.825
MPH = ((HP / Weight)^.333) * 234
Multiplying the two formulas together, we get :
ET X MPH = 1363.05
According to this relation, if we know the ET, we get the MPH. And vice versa.
For example, for a terminal speed of 159kmphr, this formula gives the ET as 13.7. Pretty much matches the figures of an RD from a drag which happened a few months back.
And important thing is - this relations tells us that we need at least 146kmphr to get under 15 secs. And thats where all the competition lies. 14-15 seconds.
So anyway flash over to Tuesday afternoon. Im browsing through the forum idly when a PM window pops up with a message asking us to come over in the evening. Here's hoping we are able to put together the engine today. Which would mean that the first test run is going to be tomorrow morning. Ok, i need to take along with me all the tools, including the dial guage. Another boozeless day, hopefully.
Well wednesday it is, and nothing much happened yesterday. Yeah was a boozeless day indeed but couldnt put together the engine, since the heads were yet to come. Handed over the gaskets etc. And opened up Toms RX head; He needed to check the port height. Found that the exhaust port was 33mm down from TDC. Anybody opening RX heads - make sure you have a 13 size bit.
And well no news for the next two days, and its on to saturday, the 5th. We are at Ron's basement and the barrels are ready,ported and the heads are shaved. First of all, we measure the head volumes. Ron produces a syringe, using which 5mm of petrol at a time is poured into the head cavity. It fills up at the third round - 15cc.
There is some discussion on the gaskets. And then we decide to use a 1.5mm thick Aluminum one. The gasket fits in, and 3-bond is loaded. The barrels go on and then the heads. Meanwhile the carbs have been taken off and are lying on the table. So we start to tighten the heads only to notice that the bolts are not holding the heads down properely. The bolts do tighten; but they dont hold down the head firmly. Reason - the 1.5mm thick gasket lying beneath the barrels. So we need washers. And to each bolt we add two washers and within an hour more, the heads are biting down hard and fast and the engine sits firmly, all done. Now effectively the port timings have been changed - equivalent to raising all the ports by around 1mm, thanks to that aluminium gasket down below. You can spot that thick gasket jutting out in this pic:
Here is a good article on engine rebuilds.
We need 165 size main jets. What lies in the carbs are 140s. But its around 9pm now, and we decide to call it a day. So me and Tom pack off on the RX, straight to the Dolphin bar near Toms place. Its Vodka, Whiskey and Rum till about midnight.
Things pick up at 3pm on sunday. The carbs are taken and opened. The jets are in bad condition. Ron offers us the 165 size jets which he have, and we promise to get him another pair soon.
We look into the carbs and see that the hole leading from the airside into the needle jet passage is blocked. So Tom gets a pair of syringes from the nearest medical shop. The thin needle does the trick and cleans out those narrow passages. We fit the carbs soon and start the bike. Doesnt sound very great; Kind of messy. I take it for a spin but i dont push it much. But in first gear, i explore a bit into the midrange and the front wheel goes right up. What scares me is that the bike is hardly set up, except for the engine.
The carbs need to be experimented with more, and same with the ignition timing. So i wonder what the bike is gonne be like once the whole thing is perfected. We check the airbox and see that the wiremesh air filter is totally junk; it doesnt have those rubber strips along the sides. Basically means its not sealed and the bike is as good as not running with a filter. We recieve strict instructions not to push the bike in anyway until the air filter is fixed and the carb needles are set at richest slot. Meanwhile a check on the ignition timing shows us something around 2 btdc. Anyway its late by now, around 9:30. So we push off, promising to fix the air filter, carb needles and timing, before we push the bike to its limits.
wondering if there is some place where i can get a genuine quality paper filter. But not really sure how it will fit in a drag setup.
I reach home and i notice that there is a strange but very visible midrange flutter. Once the rpms cross around 4k, the bike seems to fire totally ineffectively. Cant place my finger on the problem. Meanwhile good ol jaggu comes over from TGIF, and takes a spin. He notices the same thing and we spend some time pondering over it. Jaggu feels that it has got something to do with the electricals. Maybe timing is bad. Anyway sunday edges over, at the end of which the bike is back with a beautifully ported engine and we have to take it from here.
All of monday is wasted, right from early morning to 10pm, in a fullday 'team building' activity from office.
And tuesday morning it is. I get up early and around 6:30am start up the bike. Ride it till the nearby tea shop for my morning smoke/tea. Suprised to see that there is no flutter. Wondering whether it appears after a few kms of riding.
Here is a pic of the bike. Doesnt look any different, but the engine is now a monster.
Stuck in office and looking fwd to reaching home as early as possible. First plan is to change the timing. retard it as well as advance it and see the difference. As i mentioned earlier - problem is very visible; There is a horrible midrange flutter once the rpms cross 4k. And this lingers to around 6k and the bike is not showing much appetite for revvs after that point.
My guess right now at 9am is, the timing is too advanced. Should find out by 9pm. As i said, right now the timing is around 2mm btdc. Really cant imagine where to go from here.
Anyway the steps ahead can be summarized as:
b) Get the air filter sealed.
c) Experiment with Jetting. First drop the needle slot to the richest slot and see. then if needed, move on to higher size jets. basically take it as rich as it will take.
d) Once this is done and nothing can be improved more, throw away that local CDI, and switch over to points or a better CDI.
e) With the performance at the max in this setup, throw away the stock pipes and install chambers. Then do the jetting process again. Take it richer from where it was, as far as it takes.
So hopefully at the end of these steps, we should have a stage 1 bike, running chambers, with perfectly tuned and jetted carbs and a good CDI running a perfect timing. Anyway its gonna be sometime till we reach there. But its going to begin today evening.
So its evening, and im back at home. First thing i do is to take a close look at the base gasket; I find that at one point there is a layer of black oil. Wonder if this is a leak.
Next step is to inspect the plugs. I open em up and they look like this :
Bloody rich. The needle is in the one above the richest slot. Certianly looks like we need to push it down, leaner. I wonder if there is an alternative. Something to make the airflow better.
Anyway i open up the magnet cover, leaving the carbs alone. Grab a screw driver, loosen the stator plate screws and rotate the plate a few degrees anticlockwise. Retarding the timing to around 1.9mm BTDC.
I take a ride but cant notice any particular difference.
Then back to the carbs. I resist the temptation to go leaner and go the other way, just to check. I move the needle to the richest slot, fit it back in and take another ride. The flutter has increased noticeably. Its not a 'midrange' flutter as i thought - now its very apparent that the flutter wakes up around when the main jets get into action. My hands are itching to push the needle down a couple of slots and go leaner. But i guess we shouldnt do that without checking other alternatives. Maybe should think about boring out those carbs. Its getting dark by now so i stop further activity and pack up the tools.
So summary by tuesday evening is - in the present setup, the bike is running rich. And retarding the timing didnt provide any noticeable effects. Maybe the richness is masking off anything else.
Wednesday evening saw lots of rain. Did nothing except sit inside smoking and pondering about this mysterious rich condition. The porting should easily take 165 size jets; Then i wonder whats wrong. Possibilities :
a) The carb bores are just not large enough to flow enough air.
b) The CDI - its putting out too weak a spark, resulting in an incomplete combustion.
c) The airfilter is clogged. But i doubt this though; As such it doesnt even seal properely.so cant imagine any air restrictions out there.
Personally, i tend to latch on to (a) and (b). If (b) is the culprit, then no choice other than to live with it for one more month. Financial troubles. And about (a) i realize that there is a way to verify. Toms bike is running slightly overbored carbs; We just need to do a transplant. But for that we need to wait till this weekend, since its better to take some time and do it in peace.
Meanwhile on thursday evening, i come to know that my weekend bike plans have gone burst. Im pulled into another trekking trip. So i call up and Tom and we decide to have a test run the next day, friday morning.
So the alarm rings off at 5:15am friday morning. I wake up and ring up Tom. He is up in a flash and its not long before we reach the outer ring road. Basically we dont plan to do much running, just the bare minimum to get the figures. So Tom does two runs. The first one, he misses a gear; But he finishes at 124kmphr. The second run, he is careful not to push the rpms much so that no gear misses; And he finishes at 128kmphr. And we notice that the bike is easily, way easily finishing in 6th gear. Then i take it for a topspeed run, but i notice that the bike is heavily limited by the richness and stumbles around 133kmphr.
All in all, things look just too good. The needle is in the bottom slot and the bike is running awfully rich. Still it manages 128kmphr. So once the jetting is perfected, the earlier assumption of 133kmphr is just too easy. We can safely assume 135kmphr@400m with perfect jetting. Think about the local CDI fitted and things begin looking too good. Put in points or a racing CDI and the bike should cross 140kmphr, even without chambers.
Well i guess i should come back down to earth and be careful not to be over-optimistic. Ok, coming back into a realistic-pessimistic mode - right now its doing 128kmphr. Sort out the jetting, and it should do around 132kmphr, say. Throw in a racing CDI and it should get to say 135kmphr. And with chambers in the scene, we will cross 140kmphr. The above paragraph is a dream situation. This one is a scientific surety.
Anyway the weekend is lost in trekking. Back to office on monday morning. And there is not a single muscle that doesnt ache. I wish i can just drop dead. Sure doesnt look like i can do anything on the bike today evening. Im just gonna reach home and flop into the bed and am not gonna get up till tomorrow morning. But then maybe i can finish off the airfilter work. Thats something i forgot to mention. Friday evening, i had dropped at my Mechs place, and asked for those rubber strips which seal the airfilter. He searched around, and could find one. So it took it home and before leaving for the Trek, had time to fix it on one side of the airfilter. So now the filter is half-sealed. I dont have a genuine rubber one for the other side, so i need to think of improvising something and fitting it on with the help of some super-glue. Maybe this is something which i can take care off, before launching into a much needed sleep today evening.
Well back at home, i spent an hour on the airfilter. I cut up a plastic-leather belt which was lying around and managed to stick it around the bare side of the airfilter, finishing off a tube of super-blue in the process. Now the airfilter looks OK, with both ends sealed. Let me see if i can post a pic of the reworked airfilter.
After talking with Ron, the decision is to leave the CDI and jetting alone for now, and to focus on the reeds and the chambers. We need Reeds that flow better and hopefully Ron should have completed the Chamber design by now. So within two days we plan to take the bike to Rons place.
More to come....