89 Sportrak 1.6 Carb - Losing power under acceleration

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Recently bought a secondhand Sportrak 89 carb 1.6

Problems started on the drive home from collecting it. On hard acceleration, under load it 'bogs' down and misses, the revs drop back, the speed lowers and then it picks up again. Usually this happens when going past 60mph, at about 3000rpm. But can happen higher up the rev range at slower speeds with less engine loading.

The missus drove it back along the M4 last night, and it happened again. Eventually the engine didn't have enough power to move at an acceptable speed along the hard shoulder and pull away, so she stopped.

Needless to say the vehicle and the missus arrived home last night on the back of a lorry (the sportrak was on the back, not the missus).

The driver said that he suspected head gasket. I've started the vehicle tonight and it starts fine, no loss of water from the header tank. No white smoke.

It's always ticked over poorly until the alternator was rebuilt last week, now it idles fine. It has a dodgy manual choke conversion fitted (anyone know if I can revert to an automatic choke, and how to do so?).

It doesn't overheat, and runs fine apart from the foot down missing and poor running at above 60mph.

Any suggestions? I'm guessing igntion (dizzy cap, timing, plugs leads etc) any help would be greatly appreciated in solving this potentially expensive problem.

MISSING SPORTRAK.

I am not familier with the Carb models ut it doessound very much like either the ignition or fuel system that is breaking down.

Ignition. Go for the cheapest first so check the dizzy cap and rota arm for wear or cracks and tracking marks on the inside of the cap. If the rota arm is burnt at the end clean it on the wall of a tyre. If either look knackered then replace.

Leads are often ignored and breakdown over a number of years utill they fail. If you get a shock from them when the enine is running then the silicone insulation has prbably broken down. Check them for cracks and general deteriation. The carbon leads which are now used have small gaps in the carbon core that forces the power to jump and this increases its intencity. In damp weather moisture gets through old insulation and makes starting difficult and will cause power loss. There is a bloke on ebay selling new sets for under 12 quid so if in doubt replace them. Look at the state of the plugs and adjust or replace. Don't wire brush them as this buggers up the insulation of the inner terminal. If the deposits are black after a run then the car is running too rich. If the deposits are white then too weak. Each plug should have a sandy brown coloured deposit. Adjust the gaps and if any of the electrodes are eroded then replace the set. If any of the deposits are black and oiy then that cylinder is burning oil which will need further investigation.

Assuming these are all fine then check the ignition timing. Adjust if necesary. If the plugs were black with carbon then it MAY be that the timing is too far advanced making the car run rich, if they were white then the tming MAY be retarded making the engine run weak and hot. Isay may as this is one reason and you may find the tming spot on. Use a strobe to chck the timng marking the appropriate timing marks white on the pully and the appropriate fixed point timing belt cover area representing the degrees stated in the Manual or owners handbook. If these are lined up when the engine is running and the strobe pointed at them then the timing is. If they arnnt then loosten the retaining bolt at te base ofthe dissy and turn it eiter waygently until the marks align. Tighte the bolt and recheckthe marks with the strobe for allignment. Make sure youread the Manual to get the correct RPM for chacking and remove the vacuum advance tube if it says to. Once complete replace the tube and tighten the clamp on the dissy. If youfound tat you needed to adjust the timing or replace any igntion parts then run the car tosee ifthe roble persists. If it doesthe turn to the Carb.

ONCE YOU ARE SATISFIED THAT THE IGNITION SYSTEM IS OK THEN TURN TO THE CARB.
This part I am unfamilier with on Sportraks but more than familier on other normally aspirated cars. Again there will be amixture screw that will adjust the fue air mix andif you found that the timing was ok yet the plugs either white or black then the mixture will be ether too richor too lean and the mixture screw should be adjusted accordingly. Normally you turn the screw in by small amounts (The mixture screw has a tapered end that goes into the choke tube of the carb). Screw in utill the engine becomes a bit ruogh then gently screw it out until it runs smooth again screw a bit more out and it will run rough again. Allow the adjusted mix to settle momenterally before screwing in more or outmore. The best setting is in between the two. A colour tune plug would help with accuracy but because the plugs are so deep down I think it would be difficultt use. If you have an exhaust gas anayzer then this will do the job but you can do it by ear. It is possible that the float camber is flooding and forcing too much fuel into the carb. In mostcars this is like a toilet system wit a float and stop cock. If the pin on the end of the stop cock has worn with use then it allows petrol to overfill the float chamber and can lead to an enriched mixture. Carb spindles ware with age ca cause problems by not closing tightly. You can really only check this with the carb off the car. As I said I am not familier with the Carb on the Sportrak and my experience has been with SU and Zenith carbs and maybe copletely innaproprite to the Carb in question.

As for the head gasket, yesthe symptoms could be this but the car would tend to run hot and lose water.If you remove the oil filler cap and if it is full of "salad cream" then this is caused by oil and water mixing but in cold weather a sall amount of this can form due to condensation. Obviously if it is a large amount then it indicates water contamination in the oil.Look at the oil on the dipstick,is it grey?, or normal. Again grey or salad creamy points to water contamination and the head gasket.

I hope this has been of help to you and I am sure that if any part is incorrect then another forum member will correct it.

Good luck

OLDMINIMAN

M J Young

problems can't accelerate or get above 60mph

We have just bought our 12 year old 4 weeks ago 2nd hand, drove 25 miles then the cylinder head gasket blew. This has since been replaced and there is still no power and keeps revving irratically. We are unable to get power above 60mph, and it has no acceleration what so ever.
The sparks have been replaced we have checked all leads, and replaced the clutch cable, plus 4 new tyres as all were bald. what else is left?
Can any one help?

You're sure it was the head

You're sure it was the head gasket blown?

The problems with my vehicle stem directly from the carb. If your model is the 16v carb engine then the original carbs are notoriously troublesome.

I've just order a replacement carb from a breakers to try and fix the problem. I'll let you know how I get on.

Most problems with ticking over / acceleration are from poor setup/lack of airflow into the carb.

However, from the symptoms you describe (especially if the head has been off) would suggest timing?

Dodgy manual choke

Dodgy manual choke conversion?

I am already smelling a very, very large rat here.....My first step FWIW is I'd be having a poke about EvilBay and some breakers for a complete replacement carb.

Dave with a Sporty

Dave with a Sporty

I had same problem

Check carb, pull of pipe from fuel pump and use air pump to blew hard through jets, check nothing affecting jet (the idle jet sounds as though it is working), take of air filter and use pump to give jet a closer blew with pump, you can use fingers to block pipes at top individually when blewing though fuel pipe. The carb can then be easily dismantled if sounds the problem, and give a gentle clean (I was unable to find non dealer parts for carbs).
Timing unlikely to have changed unless it looks like someone has done repairs on your dizzy, however its easy to check with strobe.

best wishes